lectronics For - WorldRadioHistory.Com...*CAREERS IN ELECTRONICS PART 1 12 The first in a major new series. FAMOUS NAMES 24 Charles Proteus Steinmetz. RADIO RULES 41 Concluding with

MAY 198380p

AN ARGUS SPECIALIST PUBLICATION

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OR DIRECT- ONLY 75p, AND INCLUDING 3 x £1 DISCOUNT VOUCHERS

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Telephone (Consumer Sales/Enquiries) 0277-230909 - Telephone (Industrial Sales/Enquiries) 0277-231616 -Telex 995194 AMBIT G. Data 24hrs (RS232/300baud) 0277-232628 - REWTEL.

Prices exclude VAT except where otherwise shown. Postage and Packing 60p per pre -paid order. Orders submitted using Ambit Stock Codes will be processed first. Orders for in -stock items

despatched same day (up to 4pm receipt). Hours - (consumer sales) Sam-7pm Mon -Sat: (Industrial) Sam-6pm (Mon -Fri).

PROJECTS*STALL THIEF 20Leaves your car burglar sitting in the road.*AERIAL WITHOUT WINGS 27Converts a car window demister to long and medium wave.*HE AUTO TESTER 28An all -in meter for car electrics.*BBC MICRO/HEBOT INTERFACE 62Hobby's personal robot moves faster than ever.

FEATURES*CAREERS IN ELECTRONICS PART 1 12The first in a major new series.FAMOUS NAMES 24Charles Proteus Steinmetz.RADIO RULES 41Concluding with the Radio Amateurs' Examination.*ACES HIGH 47Meet the new Jupiter Ace micro computer.*DIY HIFI 52High quality build -it -yourself loudspeakers reviewed.THE ELECTRONIC REVOLUTION 57Electronics go micro.

SPECIALS*SPECIAL OFFER 10PCB -maker's kit at 1982 prices.

REGULARSMonitor 6What's On Next 18HE Bookshelf 33Buylines 34Points of View 36Clever Dick 39HE Subscriptions 55HE Backnumbers 68HE PCB Service 71HE PCB Printout 72Classified Advertisements 73

Editor: Ron KeeleyEditorial Assistant: Helen Armstrong BATechnical Illustrator: Jerry FowlerAdvertisement Manager: Jolyn NiceDivisional Advertisement Manager: Gary PriceManaging Editor: Ron Harris BScManaging Director: T.J. Connell

DO IT YOURSELF - page 52

CAREERS IN ELECTRONICS - page 12Picture courtesy of British Telecom.

BBC/HEBOT INTERFACE - page 62

Hobby Electronics is normally published on the second Friday of the month prior to the cover date.Hobby Electronics, 145 Charing Cross Road, London WC2H OEE, 01-437 1002. Telex No 8811896. Published by Argus Specialist Publications Ltd.

Design and Organisation by MM Design and Print Ltd, 145 Charing Cross Road, London WC2H OEE, 01-437 1002.Distributed by S. M. Distribution Ltd, 16/18 Trinity Gardens, London SW9 8DX.

Printed by QB Ltd, Colchester. Covers printed by Alabaster Passmore.Notice: The contents of this publication including all articles, designs, plans, drawings and programs and all copyright and other intellectual property rights therein

belong to Argus Specialist Publications Limited. All rights conferred by the Law of Copyright and other intellectual property rights and by virtue of internationalcopyright conventions are specifically reserved to Argus Specialist Publications Limited and any reproduction requires the prior written consent of the Company. All

reasonable care is taken in the preparation of the magazine to ensure accuracy, but Argus Specialist Pulications Ltd cannot be held responsible legally. ©Copyright1982 Argus Specialist Publications Ltd. Member of Audit Bureau of Circulation.

Hobby Electronics, May 1983 3

electrontze AUTO -ELECTRONIC PRODUCTSKITS OR READY BUILT

r ELECTRONIC IGNITION

1.

11110(110Tthetifestqn

IS

YOUR CARAS GOOD AS IT COULD BE ?* Is it EASY TO START in the cold and the damp? Total Energy

Discharge will give the most powerful spark and maintain fulloutput even with a near flat battery.

* Is it ECONOMICAL or does it "go off" between services asthe ignition performance deteriorates? Total Energy Dischargegives much more output and maintains it from service toservice.

* Has it PEAK PERFORMANCE or is it flat at high and low revs.where the ignition output is marginal? Total Energy Dischargegives a more powerful spark from idle to the engines max.(even with 8 cylinders).

* Do the PLUGS and POINTS always need changing to bringthe engine back to its best. Total Energy Discharge eliminatescontact arcing and erosion by removing the heavy electricalload. The timing stays "spot on" and the contact conditiondoesn't affect the performance either. Larger plug gaps can beused, even wet or badly fouled plugs can be fired with thissystem.

Is the PERFORMANCE SMOOTH.The more powerful sparkof Total Energy Discharge eliminates the 'near misfires'whilstan electronic filter smooths out the effects of contact bounceetc.

Most NEW CARS already have ELECTRONIC IGNITION.Update YOUR CAR with the most powerful system on themarket - 31/2 times more spark power than inductive systems -

3'htimes the spark energy of ordinary capacitive systems, 3times the spark duration.

Total Energy Discharge also features:EASY FITTING, STANDARD/ ELECTRONIC CHANGEOVERSWITCH, LED STATIC TIMING LIGHT, LOW RADIOINTERFERENCE, CORRECT SPARK POLARITY andDESIGNED IN RELIABILITY.

* IN KIT FORM it provides a top performance system at less thanhalf the price of competing ready built units. The kit includes:pre -drilled fibreglass PCB, pre -wound and varnished ferritetransformer, high quality 41F discharge capacitor, case, easyto follow instructions, solder and everything needed to buildand fit to your car. All you need is a soldering iron and a fewbasic tools.

FITS ALL NEGATIVE EARTH VEHICLES6 or 12 volt, with or without ballast.

OPERATES ALL VOLTAGE IMPULSE TACHOMETERS:(Older current impulse types need an adaptor).

STANDARD CAR KIT £15.90Assembled and Tested £26.70

TWIN OUTPUT KIT £24-55For Motor Cycles and Cars with twin ignition systems

Assembled and Tested £36.45

PLUSP. Et P.

£1 (U.K.)

PricesincludeVAT

PROTECTYOUR CARWITH ANELECTRON=ELECTRONIC ALARM* 2000 COMBINATIONS provided by an electronic key - a

minature jack plug containing components which must matcheach individual alarm system. (Not limited to a few hundredkeys or a four bit code).

* 60 SECOND ALARM PERIOD flashes headlights and soundshorn, then resets ready to operate again if needed.

* 10 SECOND ENTRY DELAY allows owner to dis-arm thesystem, by inserting the key plug into a dashboard mountedsocket, before the alarm sounds. (No holes in externalbodywork, fiddly code systems or hidden switches). Re -closing the door will not cancel the alarm, before or after itsounds, the key plug must be used.

* INSTANT ALARM OPERATION triggered by accessories orbonnet/boot opening.

* 30 SECOND DELAY when system is armed allows owner tolock doors etc.

Don't Wait UntilIts too LateFit one NOW!

* DISABLES IGNITION SYSTEM when alarm is armed.

* IN KIT FORM it provides a high level of protection at a reallylow cost. The kit includes everything needed, the case,fibreglass PCB, CMOS IC's, random selection resistors to setthe combination, in fact everything down to the last nut andwasher plus easy to follow instructions.

FITS ALL 12 VOLT NEGATIVE EARTH VEHICLES.SUPPLIED COMPLETE WITH ALL NECESSARY LEADSAND CONNECTORS PLUS TWO KEY PLUGS

CAR ALARM KIT £ 24.95

ASSEMBLED AND TESTED £ 37.95

PLUSP. & P.

£1 (U.K.)Prices

includeVAT

2111.e.,.e-

Access and VisaWelcome. Write orPhone Quoting Number

ELECTRONIZE DESIGNDept . E Magnus Rd Wilnecote

Tamworth 877 5BYtel: 0827 281000

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MONITORWill The Last Person To LeaveThe House Kindly Put It OnStandby . . .

The futurist's dream (one of themanyway): your house at your command.You describe the environment you want,and the computer does the rest. Eventual-ly, not even a computer like the microswe're playing with now, but a littlemachine totally dedicated to controllingyour habitat at the press of a button, nay,at a spoken word. We're not quite thereyet, but the incidence of units eitherspecifically designed for controllinghousehold processes, or readily adap-table as such, is definitely increasing.Here are two:

First, from Electronic and ComputerWorkshop, a Universal MicroprocessorTimer. Developed originally for industrialand lab use, it comes in kit form suitablefor hobbyists. Applications specificallymentioned by ECW include control ofhouse lighting, TV/audio gear, andautomatic plant watering.

The timer is based on a pre-programmed TMS 1000 microprocessor,and has a 24 -hour clock with four in-dependent relay -controlled outputs.There are 20 daily/weekly functions,entered via a keyboard, and the timer canbe set to control any one of the four relayoutputs.

Timer functions are set out clearly andsimply in the manual, and completedsteps are indicated by LEDs and a 1 2mmseven -segment LED display.

The unit's power supply is stabilisedon a separate PCB, and one output controlrelay is supplied. A total of four relays canbe accommodated and relays can be easi-ly obtained.

The kit comes complete with printedpanel, to be installed as either a built-in orfree standing unit. Price is £58.06(complete with wooden housing) plus15% VAT plus £1.50 p&p. Orders andenquiries to Electronic and ComputerWorkshop Ltd., 171 Broomfield Rd.,Chelmsford, Essex CM1 1RY. Tel:(0245)62149.

Secondly, Superswitch Electric Ap-pliances ("Total control at your Finger-tips") has come up with the CommandCentre, a 'revolutionary' new remotecontrol unit for all kinds of electrical ap-pliance.

By transmitting high frequency signalsalong AC mains wiring the CommandCentre is capable of remotely operatingup to sixteen different appliances.Remote control can be done eithermanually or programmed to take placeautomatically up to seven days ahead,with a maximum of 24 automatic pro-grams at one time.

The signals sent by the Command con-sole are received by plug-in modules,designed either for appliances or for por-table lamps, which are plugged into theoridinary 13 amp household sockets. Thetwo types of module are a safety feature,as one kind is rated for loads up to 13amps and the lighting one for tungstenlighting up to 400W.

A major feature of the Centre is its

ability to check and indicate whether anappliance in another room is on or offwhen asked. Other features include an'energy save' key to bring on lamps at oneof three brightness levers; manual dimm-ing of lamps; ability to turn on all lampssimultaneously; simple programming on akeyboard that gives tone to tell you thatentries have been correctly made; choiceof 12 or 24 hour digital clock; simplereviewing and alteration of programs; 9Vbattery to save programs in case of powerfailure; ability to turn off up to twelvemoduels simultaneously; filter modulesavailable in case of any interference to theCommand Centre from some TV sets;manual override on all modules, and lastbut not least you can use it as an alarmclock.

The price for a 'starter pack' with theCommand Centre, and one of eachmodule, is £139.95 inc VAT, no p&p.Contact Superswitch Electric AppliancesLtd., 7 Station Trading Estate,Blackwater, Camberley, Surrey GU179AH. Tel: (0276) 34556. Superswitch,incidentally, do all kinds of domestic andlight industrial timer controllers, dimmer

and time delay switches, remote controlswitches and units, fan controls andsecurity switches.

Slick Scope Probes

More closely resembling a super ex-ecutive non-slip-grip-fibretip pen than aconventional scope probe, Greenpar Con-nectors' new range of Posiscan inexpen-sive miniature oscilloscope probes havebeen designed for easy and accuratehandling on crowded PCBs. The probescome supplied with seven accessories: aBNC adaptor for signal aquisition from a

co -ax socket, an IC test tip, . up insulator,detachable earth lead, spring hook, trim-mer tool and a spare probe tip in case ofaccidental damage to the hardwearingoriginal. 1.5 metres of cable is supplied.

The probes are compatible withHewlett-Packard, Philips and Tektronixaccessories. Two types are available: No.99025, with 10:1 fixed attentuation,and No. 99125, with attenuation swit-chable from 10:1 to 1:1.

The specifications give, for the 10:1probe (both models): bandwidth morethan 250MHz giving useful bandwidthfrom 100 to 140MHz with typical 100 to150MHz scopes; risetime 1.5ns max.;compensation range for scopes of 15 to50pF input resistance; input capacitance1 5pF nominal (1 7pF for the 99125); in-put resistance 10MR ± 1% with scopesof 1 MR resistance; for the 1:1 probe(991 25 only), bandwidth 5MHz; risetime7Ons; input capacitance 100pF; inputresistance equal to scope.

The probes come packed in a new -style card carton with the specificationprinted on the back. Prices are around£18.00 and £20.00. For further infor-mation contact Greenpar ConnectorsLtd., Studlands Park Avenue,Newmarket, Suffolk CB8 7EA. Tel:(0638)668081.

Status Quo Fans Please Note

If you use any number of ICs and find thatthey come out of their packaging withtheir legs splayed out, so that they do notmatch standard IC plugs or rub -down PCBmarks, Aries Electronics have a toolwhich will restore proper alignment.

The Dip-R-Sizer T-516 is designed totake ICs with both .003 or .006 centres.The IC is simply mounted on one side oranother of a metal block between a pair ofsprung jaws, and the legs squeezed backinto specification.

It doesn't look as if the tool would bemuch help if your 'carpet crawler' hasbeen trodden on or squashed right out ofshape, other than giving the legs a finaladjustment to the right pitch after aworkout with the pliers.

Most useful if you're sharing aworkshop or lab, at school for instance, orif you are cannibalising a lot of stuff fromold boards. Price is £10.50 inc. VAT andP&P.

Aries Electronics (Europe), Eastways,Witham, Essex CM8 3YQ. Tel. (0376)519318.


MONITOR

Spectriim Joystick

A self -centering joystick, called theCompetition -Pro, is now available for theZX Spectrum from Kemston Micro Elec-tronics. The compact unit has eight direc-tion commands and two large fire buttonsfor ease of play without wearing out yourhands too quickly. Furthermore a numberof software houses are developing gamesfor use with a joystick, and others are onthe way. It should also be possible to con-vert any BASIC program to work with thejoystick and a short program is included toshow you how to do this.

The joystick has a boxed interfacewhich simply plugs into the expansionport of the Spectrum, with or without theprinter.

Price is £25.00 plus £1.00 pEtp. En-quire Kempston (Micro) Electronics,180a Bedford Road, Kempston, BedfordMK42 8BL.

Memories Of A Camel

More memory modules from Camel Pro-ducts: for the ZX81, a new 64K RAM ex-pansion modules. This comes with a linkoption to disable RAM in the 0 to 16Krange of the ZX81 's memory (for use byperipheral cards) and is therefore able toaccept an EPROM as an alternative in thatpart of the map. A 28 pin IC socket canaccomodate not only the popular2716/2732 EPROMs but also the newer2764 and 27218 devices. These lattergive the user 8K and 1 6K of non-volatilememory respectively.

The cost per byte of the 2764 isalready nearly as low as the smallerEPROMs and they are seen as an impor-tant trend for ZX81 program storage.Another link option allows slow (450ns)EPROMs to be used with a slightly higherpower dissipation.

The unit, named DREAM 81, comes inan ABS case with LED power indicatorand costs £69.95 plus VAT.

Secondly, Camel have introduced a 4Kversion alongside their 2K MEMIC LCMOS RAM unit. The new MEMIC L 2 of-fers as much memory as the 2732 and2532 Eproms (See HE March '83). Theseunits use the latest True CMOS staticRAMS which take only a fraction of a uAof current to retain data. An integral

Hobby Electronics, May 1983

lithium battery supplies the standbypower for ten years or so and the currentdrain is so small that no battery on/offswitch is needed.

The use of fast (200ns) RAMs extendssystem capability by providing a user -definable ROM which can run withoutwait states in most systems and yet canbe reprogrammed at will. This is useful asa soft character generator, for extendinglanguage interpreters and operatingsystems, etc.

The MEMIC unit comes in a mouldedblack AMS case with a flip -open windowfor a 24 pin cable connector, the far endof which plugs into the host system's2716/32 or 2516/32 socket.

Price is £35.95 plus VAT. For infor-mation contact Cambridge Microelec-tronics Ltd., 1, Milton Road, Cambridge.Tel:10223) 31814.

Never Mind The Voltage,The Heat

Feel

Anyone who has access to a digitalmultimeter can now use it as a wide rangetemperature measuring instrument usingstandard type K thermocouples, by ad-ding Graham Bell Instrumentations'DVM/TC Interface Unit.

At considerably lower cost than adedicated unit, this device has atemperature range of - 50° to 1100°Cand incorporates automatic cold junctioncompensation. Thermocouples are at-tached via a miniature compensatedsocket. A basic thermocouple and matingplug are supplied as standard with the in-strument.

The output of 1 mV per degree cen-tigrade is via a 0.75mm coiled lead fittedwith 4mm plugs. Long term stability is ex-cellent and the low battery drain allows itto be used for continous monitoring ifnecessary. Since the accuracy is not af-fected by the output loading, it may alsobe used to interface low output im-pedance instruments such as chartrecorders.

Price is £36.00 plus VAT. For more in-formation and p&p charges contactGraham Bell Instrumentation, PO Box230, 39 Derbyshire Lane, Sheffield S80TH. Tel:10742) 582370.

A Bit More Scope

The Philips 1 5MHz PM3207 oscilloscopenow incorporates a new CR tube which(like so many advances) is simpler indesign yet more reliable than earliertubes, and gives a sharper and brighterpicture. Using their renowned colour TVexperience, Philips have used simpleinternally -mounted permanent magnetsto manipulate the electron beam, ratherthan the conventional electrostaticsystems, and two permanently -magnetised wire rings are fitted in theelectron gun, giving greater, and bettercalibrated, deflection sensitivity, moreaccurate beam centring, stigmaticfocussing and more accurate scanning; ahigher acceleraton voltage is possiblethan usual in this class of scope, giving abrighter picture.

The choice of display modes includesA + B vertical channel display withseparate B channel inversion, and Xdeflection through the A vertical inputchannel, for maximum input sensitivity inthe X -Y display mode. Automatic trigger-ing is standard; a separate peak -level con-trol ensures a stable picture and the in-tegral TV triggering facility providesautomatic changeover from line to frame.Sensitivity is high (5mV), and there isdouble insulation between line and scopeto avoid ground loop problems. Thedisplay screen is 8 x 10 cm, weight is 5kgand dimensions are 300 x 130 x 37mm(12 x 51/4 x 14%in). The PM3207 isadvertised as meeting all the environmen-tal requirements of a heavy-dutyworkshop oscilloscope, to standard VDE0411 (a European standard).

Price is £372.00 from retail outlets, orcontact Pye Unicam Ltd., York St., Cam-bridge CB1 2PX. Tel: (0223) 358866.

7

Group, 1 Marlborough Drive, Worle,Avon BS22 ODQ. Tel: (0934) 21315.

The radio wristwatch shown in our pic-ture uses a Ferranti Electronics ZX414Ztuned frequency circuit. The watch ismade by Advance Products UK Ltd., 8AHornsey St., London N7. Tel: 01 6090061. Well, it's a change from the per-sonalised stereo suitcases seen and heardso oft upon our streets . . .

The Super Electro analogue multi -meter from Elemic of Italy is now beingsupplied by Black Star. Voltage can bemeasured to 1000VAC and DC, andcurrent to 30ADC and AC, as well asresistance and capacitance. The SuperElectro also provides phase sequencedetection for three phase systems and amains and insulation tester. It is basedon a high precision moving -coilammeter, and has coloured scales, anantiparallax mirror and comes completewith a lined protective case, fused testleads and one year guarantee.Sensitivity is 20kR/VDC, accuracy is1.5% fsd, and there is 50,000V protec-tion on all ranges.

The Super Electro costs £39.95 plusVAT from Black Star Ltd., 9A Crown

4/ lb

4000.0""""'

super eiectro

.4%." dr.**. 0 A"4400v

WO V 61 0

,

NY, aax protected

MONITORShortsStotron are now supplying solderingequipment by Greenwood: this includes ahigh quality 24V 50W soldering station, acordless Iso-Tip iron powered by long lifeNiCad batteries (a real boon to anyonewho indulges in modifications to their caror bike electrics), which automaticallyrecharges itself overnight in its own, plug-in stand, and accessories includingsolder -suckers, de -soldering braid andiron -coated long -life soldering tips.

For information on both these rangescontact Inge Abraham, Stotron Ltd., 72Blackheath Rd., Greenwich, LondonSE108DA. Tel: 01 6912031.

OK Machine and Tool are doing a rangeof PC board guides and brackets in mould-ed black plastic, to accommodate boardsfrom 1.02 to 2.55mm (0.040 to0.100in) thick with an overall length of106mm (4.12in). Snap -in buttons en-sure easy assembly to rack or brackets.The guides give a unique spring actionwhich dampens shock and vibration. Thesupport brackets feature a stabilizing postwhich permits secure mounting with onlyone screw. The guides can be bought as akit (TRs-2) which includes two guides andtwo mounting brackets. Enquire OK In-dustries UK Ltd., Dutton Lane, Eastleigh,Hants S05 4AA. Tel: (0703) 610944.

The Tangerine Users Group has movedto new premises near Bristol. This goeswith an increase in staff, the formation ofa new R Et D team to extend the Microtansystem support, and the eventual setting -up of a monthly meeting centre formembers.

By the time you read this, TUG shouldbe well settled in and the disruption caus-ed by the move should be settling down,but if anyone has written and not receiveda reply, this is the cause.

The new centre is a few miles south ofBristol with easy access to the M4 andM5, and hopefully will make a bettermeeting place for members.

The new address is: Tangerine Users

St., St. Ives, Huntingdon, CambsPE17 4EB. Tel: (0480) 62440.

Sinclair Research is marketing itspopular ZX Spectrum micro through awider chain of retail outlets from mid -February. Selected branches of Boots,Curry's, Greens and John Menzies willjoin the former sole distributor, W.H.Smith, and Sinclair's UK distributor,Prism Microproducts, will be distri-.buting to John Lewis, House of Fraser,Rank Xerox and many smaller stores.

Sinclair expects to be selling twelve tofifteen thousand Spectrums a week inthe UK by Easter, and claims sales of itsestablished favourite, the ZX81, of30,000 a week. Production of theSpectrum is now claimed to be over50,000 a month and rising, whichshould cover demand and remove thelikelihood of further distributionproblems such as Sinclair suffered in1982.

Enquiries about the Spectrum, ZX80and ZX81 to your local dealer or toSinclair Research Ltd., 25 Willis Rd.,Cambridge CB1 2AQ. Tel: (0223)353204.

All-round tool suppliers Toolmailhave now issued their new cataloguewith prices from February to December1983. The 128 page catalogue costs£1.00, including postage, and is colourillustrated with over 2000 items, detailsand prices. Delivery is free and goodsare normally despatched from stockwithin 48 hours. Toolmail prefer to buyBritish tools where possible, and offer a'no quibble' guarantee on all their lines.The new catalogues each include three£1.00 vouchers redeemable againstorders.

Contact Toolmail (1983) Ltd., P 0Box 46, Maidstone, Kent ME15 8EQ.Tel: (0622) 682861.

Hardware and heatsink suppliers Dau(UK) Ltd. and specialist in passivecomponents Church House Com-ponents Ltd., of Bognor Regis, havecombined operations to become DauComponents Ltd., and the address tocontact is 70-74 Barnham Rd.,Barnham, W. Sussex, P022 OES. Tel:Yapton (0243) 553031.

Look Sharp

Sharp Electronics have announced aseries of new products which they willshow at the 'Which Computer' show atthe NEC, Birmingham in January 1983.

They are launching a pocket com-puter, the PC1252, at the show itself.Running a version of BASIC extendedfrom the PC -1211, including two -


ONITORdimensional arrays and full string handlingcommands, it has a capacity of 24k ROMand 4.2k RAM. The memory is protectedby a battery backup when the machine is

switched off, and the PC -1251 works forup to 300 hours on one battery. It has aQWERTY keypad and 24 character LCD,and measures in at approximately 131 x19 x 9 mm. (514 x23/4 x 3/6"1.

Also available for this new computer isthe CE -125 integrated printermicrocassette recorder: the twomachines stacked together are only aslarge as a one -inch thick A5 paperback.

For the future, Sharp will also be show-ing their hand-held micro, the PC -1 500,for the first time with the new RS232 in-terface, which will allow the PC -1 500 tocommunicate with other computerseither directly or across telephone lineswith an acoustic coupler.

The PC -1 500 runs BASIC and incor-porates 16k bytes of ROM with 3.5kRAM expandable to 11.5k. Optional is anadd-on four colour printer cassetteinterace which offers automatic program,data and calculation printing.

Another Sharp preview will be an inno-vative ink jet colour printer, capable ofprinting in seven colours to produce animage of 120 dots per inch, suitable forprintouts from high -resolution colourmonitors. Futher details from Sharp Elec-tronics (UK) Ltd., Sharp House, ThorpRd., Manchester M10 9BE. Tel: 061 2052333.

Read and Write

Cassandras among us predict a major andpossibly terminal (ouch) conflict betweenthe Printed Word and the Data Store asour main source of ready reference in thefuture. New software house Ramsoft,however, is backing both horses. It's pro-ducing software with full listings publish-ed as conventional books.

Ramsoft argue that "you need booklength documentation in order to explainthe intracacies . . " (one thing is certain- editors won't go out of fashion whilethe printed word survives, if only in pressreleases) " . . . of the code and to providesufficient discussion to enable the readerto take their own programming further.And if you are in the least bit lazy you'llwelcome the fact that you can run theprograms without laboriously typing inlines and lines of code."

You can't say fairer than that. So far,Ramsoft does tapes to go with the follow-ing books: 'The Art of Programming the1 k ZX81 'The Art of Programming the16k ZX8 1 ' (both by Mike James and S MGee and published by Babani) and 'TheSpectrum Book of Games' (by MikeJames, S M Gee and Kay Ewbank),published by Granada, with more titles forthe Spectrum, Dragon and BBC Microscoming up from the same publishers in thefuture.

For more information, contact Ram -soft, P 0 Box 6, Richmond, N. YorkshireDL10 4HL.

HE

* * SATURDAY BARGAINS * *1MOS SATURDAY SALES

Starting February 12th we will be open from 10am to 4pm everySaturday to sell our vast range of components at bargain prices.You will easily find us in Daventry on the A45, opposite the John

O'Gaunt Hotel.

MIXED BAGS

Lieu available

100 Ceramic capacitors30 Axial electrdytics30 Radial dectrolytia15 Plastic capacitors20 Transistors - plastic

12.00£2.50£2.50£1.50£1.50

Only breed new and useful values included

I4 'Vv

aq

1 CMOS

TRANSISTORS

AC 107AC 126AC 188ACY 17

ACY 19

BC 149BC 159BC 171BC 173BC 212BC 2121BC 2131BC 237BC 308BC 327BC 337BC 558

4000 10p4001

top9P4002

400749136 3125pP

4008 29p40094010

4499pP

T4011 139pp

401240134014 637p

440:01165 53394p5:

4018 51p4019 21p4020 37p4021 37p4022 35p4023 10p

40254024 10p02p

4026 125p4027 17p4028 66p4029

alp4031

36:40304031 99p44003332 13905pp

4034 125p4035 40p4036 239p4038

3969pP40404041 36p

4942 56IP4043 6p

4844 5PT45 1330p40

41 6 7935pP404740413 35p

30p30p27p66p65p

BF 115

BF 194BF 197

BF 198BF 199

SMALL ALUMINIUM ELECTROLYTICS:

Axial Leeds: Radial Leads:uF V Price: uF V Price:

100022

10022

4704.7330680

6.3 15p

10 05p10 05p16 05p16 15p25 05p25 15p25 25p

29p13p13p

13p15p

7p BFR 40 20p12p10p BFX 29 25p

10

9p BFY 90 60p9p9p 2N 706 15p

12p 201131 20p13p 201132 20plop 2022224 20p13p 202369A 15p

14p 203702 10p

4049 33p4051 41p

4052 45p4053 45p4054 106p4055 123p4056 127p4063 93p4066 39p4068 12p4069 12p4070 19p4071 19p4072 10p4073 19p4075 lop4076 72p4077 19p4078 12p4081 12p4082 19p4086 50p4089 172p4093 18p4094 136p4095 93p4096 53p4098 93p4502 55p4503 59p4507 37p4508 37p4510 69p4511 ggp4512 63p4514 99p4515 172p4516 69p4518 69p4519 25p4520 96p4521 80p4526 55p4527 99p

4528 42p4532 45p4539 80p4543 99p4555 49p4556 49p4566 99p4584 56p4585 70p

253705203904204061205172205179

10p15p10p15p30p

470 16

1000 25

220 40470 4047 504.7 63

100 63

220 63

15p25p25p25p10p05p

15p20p

VOLTAGE

REGULATORS

P.S.U. COMPONENTS

TMS2516J4 8 ' 2K EPROMTMS4030JL 4K RAM8255 P.I.A.253055

Panel mounting 20mm fuseholdersContinental relays 2p clo 24V or 489Heavy duty relays - 5A 2p clo 24V

E14.90£3.00£1.90£0.35

20p50p65p

Microswitch - V type - push on terminals 25p

74 TTL

g74457446O 7447

IC> 7448C> 7450C> 7451C> 7453Cle 7454IC> 7460

747074727473

1 474747475

74007401740274037404

7405740674077408740974107413741474167417742074227423742574267427742874307432743374377438

744074427444

9p

9p

9p

10p10p13p24p24p12p22p12p14p15p16p16p13p17p23p23p23p15p15p12p15p19p17p15p

10p26p

5581p45p33p38p22p14p22p13p14p26p26p26p16p19p

7476

748274837485748674887490749174927495749674100741077412174122741287413274141741457415074151741537415474155741597416074161741627416374164741657417474175741827418574191

7419274195741997422174284742987436674368

29p55p62p69p26p

140p17p47p23p34p57p72p19p30p27p20p28p73p35p45p32p49p40p32p65p38p32p69p69p35p40p67p17p40p80p40p40p52p72p49p

140p90p28p28p

LARGE ELECTROLYTICS:

. Computer Grade.

. Made by Sprague or General Electric

. Ideal for power suppliesFollowing values available:,185,000 @ 15V300.000 @ 7V120,000 @ 15V100,000 @ 30V

71,000 @ 40960,000 @ 409

9,000 @ 50V. Prices fantastic value at only 62.50

each.

56

+Mr

59

+129+121/129129

.159159-249

IA1.5A

IA1.5A

0.5A0.5AI.5A

IA1.5A

IAIA14

2043471120912062581250w)400rnW Zeners723203055

00220T03T0330TO3

1022010220TO3

10220TO3

102201022010220

Postage and packing1 or 2 capacitors - 61.003 or more -01.50

40p140p40p

190p35p35p

140p .co40p

190p40p40p70p

150p180p

5p30p35p

BENCH POWER SUPPLY

See constructional article in February '82"Practical Electronics".

Available in kit form or built up.

Prices line VAT p + 0:

Kit Built044.00 072.00

74LS

ISOO

LSO1

1502LSO3

LSO4

1505LSO8

1509LS10

LS11

LS12

LS13

LS14LSI5LS20LS21

LS22

LS26LS27

LS28

LS30LS32

LS37

LS40LS42

LS47

LS51

LS55

LS73

LS74LS76

LS78

0

9p

9p

9p21p21p21p10p10p10p10p10p13p19p22p10p22p22p12p22p12p10p1 1 p

1 1 p

12p25p32p22p22p27p14p27p27p

[SOSLS86LS90

LS93

LS95

LS107LS109LS112

LS113LS114LS123LS125LS138LS151LS153LS156LS157LS160LS163

LS174LS175LS191

LS192LS194LS195LS197LS241

LS242LS257LS266LS2956LS298LS366LS374LS395

36p14p20p21p35p40p27p27p27p27p32p20p22p35p35p33p25p32p34p38p36p33p33p31p31p

44P49p54p28p16p70p711p

25p45p84p

orOIOIOICx<=ts

CI

01

Dept 2D, High March, Daventry, Northants N N 11 4HQTel: 03272 5523 Telex: 311245 GRENEL G

Please add 50p per order postage and packing(except where higher is indicated) plus 15% VATon total. No VAT on overseas orders, postage atcost. Cheques and postal orders made payable toEmos Limited. Send Large S.A.E. forcomprehensive catalogue.


SPECIAL OFFER TO HOBBY ELECTRONICS READERS

ON MI MN MN MO all IN MN MS In ON IN In MIS Ell Wit

g To: HE PCB Kit Offer, Argus Specialist Publications Ltd,I 145 Charing Cross Road, London WC2H OEE.

I Please send me:PCB kits @ £9.50Total

I Price includes VAT and postage and packaging.I I enclose cheque/postal order, made payable to ArgusI Specialist Publications Ltd, forI ORI I wish to pay by Barclay/Access. Please charge myI account number

Signature

1 Name(BLOCK CAPITALS)

I Address(BLOCK CAPITALS)

I Please note that this offer is

IS

valid for the UK mainland II

only. Allow 28 days for delivery.

mri so No Nu as me um In we NI so ma No aft

PCB Etch Kit for HE PCBSnow available in 1983at the 1982 price.

*Sena GS PCB Etching Kit

*Etch Resist Pen

*Polyfix Cleaning Block

*Two 6" X 4" single -sided

copper -clad boards

ALL FOR £9.50*!!No mess, no fuss.The Seno GS printed circuit boardetching system provides a high level ofsafety, convenience and efficiency formaking one-off PCBs at home or atschool. It is unique in allowing theetching process to be carried out in asealed bag, eliminating the dangerand mess associated with open tanksor baths.The Seno GS kit consists of a sealableetching bag, granulated etch chemi-cals, leak -proof box and neutraliser. Asa special bonus, this offer (availableonly through Hobby Electronics)includes an etch -resist pen that allowsyou to draw foil patterns directly ontothe copper surface; a polyfix block forcleaning the copper both before andafter etching; and, to get you startedquickly and with minimum bother, two6" X 4" single -sided copper -cladboards.

Make the most of the projects inHobby Electronics by makingyour own printed circuit boards!*Price includes VAT and postage and packaging; please allow28 days for delivery.


To51,0,

CARBON FILM6% HI -STARLOW NOISE100 to 10MftVV E24 2p

150/ 024 2'hp1W E12 GE2W E12 12p

METAL FILMULTRA STABLE

0 4 EXTRALOW NOISEIOR tp 11NR2% E24 5p1%E24 Sp

LOW OHMICGLAZE YIW0 220 to 8 211

E24 110

WIREWOUNDON CERAMIC612 SERIES

Ito 3 WATT0.220 63300 28p4 to 7 WATT0.470 to 615 33p10 to 11 WATT10 to 33K 37p

POTS bPRESETS

ROTARY POTSLOW NOISE

'A SPINDLESE3 SERIES407 to 2M LIN 32p407 to 2M

LOG 32pAs above withDP mainsswitch 79pAs above stereoInn swath/ 89P

PRESETS PIHERIDUSTPROOF163 1010 to 10M0Mini Vertical 159Mini Hrontal 16pStandard Vert 18pStandard Hone

1(10

CERMET 20TURN PRECISION

PRE-SETSNi" E3 Series

5031 to 5006 89P

CAPACITORS

CERAMIC 100VDISC (PLATE /

E12 MICRO MINItypically

1pF ro lOnF 7p

2 2 100 11p2 2 350 30p33 25 10p33 40 11p13 63 12p4.7 16 804.7 25 994 7 40 1104 7 63 12p4 7 100 14p10 25 BP10 40 I2p10 63 1110

10 100 16p

Fd

22 2V5

22 40rip14p

22 63 lOp22 100 21p47 25 top47 40 17p47 63 26047 100 28p100 18 14p100 25 16p100 40 22p100 63 250ICC 100 300220 10 16p220 16 17p220 25 22p220 40 25p220 63 30p220 100 41/p470 16 22p470 75 28P470 40 33p470 63 43p470 100 60p1030 16 30p1000 25 3801000 40 46p1000 63 8502200 16 40p2200 25 63p2200 40 70p2200 63 114p4700 16 75p4700 25 8911

RADIALS I PCBwires one end)Matsushita only.

,Fd V10 16

22 1022 1647 1047 16100 10103 16

220 10220 16

470 10470 , 161000 101000 161200 10

2100 16

6Pfip7p70809p

10prip12p17018020p24p34p44p

Single sided1CO 160 1.%100 220 1 %203 114 1.%233.230 199Double sided100 x 160 1.%100. 220 2.16203 . 114 221233 220 4.58Developer forabove ido not useGnMion Hydroxi

iiiiiiilgiiiPrices per MetreSolid connectingwire

TRANSFORMERS

POLYCARB 5%SIEMENS 7.5rnmMINI BLOC 612

25(IVInF to 6n8 7p8172 to 47oF56nF to 150nF 10p100V103nF to 150nF

11p180nF to 270nF

14p330n F to 3303n F

470nF to 560nF20p26p

680nF 30p1,,F lOmml 35P

POLYESTER250V RADIAL

1C2801lOnF, 15nF, 22nE,33nF, 47nF, 68nF,100nF 70150nF. 2.2017F 1

330nF, 470nF 1

680nF 18922p

1,5,2,2 39p

FE EDTHROUGHlnF 5000 7p

HIGH VOLTAGECapacitors

please enquiremany 60es in

stock

TANT BEADS

1 35V 14o22 35V 14p33.350 14047,350 14p68 35V 140TO 35V 14p2.2 35V 14p3.3'35V 18p4.7 16V 18047/350 200613i 25,/ 20p6.8.350 21p10'160 18P10/350 27p15/100 22p15/16V 300151250 32p22 / 6.3\/ 28022160 29p33. ION/ 30p4713V 14p47.630 34p47'16V 39p100 13V 32p100 11),/ 55P

All 240V Pruner6-0 60, 9 0.90,12.0 12V,

0

103rnA 95pIA 290

20 0 20V1.25A C2 90

12 0, 12.0SOYA 0 36

12-0 12.0100VA 8.95

0.6 6. 9.91.25A 4.25

These goods areheavy send extra

P&p We willcredit any

difference.

Se

Mains/SpeakerCableTwin 1 amp 1111

Twin 2'-, amp 16p3 Core 2 T, amp

18P3 Core 6 amp 31P3 Core 13 amp

56pScreened Cable50910 lipStereo 27pMini Srogle 12pMini Stereo 15P4 Core 4 Screens

44p4 Core 1 Screen

54p8 Core 61p12 Core 80pAerial Cable502 RG584 36p75!! UHF 36p751! VHF 28o3001/ Fla/ 14p

Rainbow RibbonCable

Prices per loot

8 VVav 19p10 Way 21p16 Way 30p20 Way 38p24 Wav 47P30 Way 5432 Way 57p40 Way 72p

RECHARGEABLEBATTERIES

VT Rt_tHOARD

0 1- COPPERTRACKS

2.5 3 75 80p2 5 5 90p3 75 3 75 90p3 75 . 5 1030

13'

280115. " 17

4.79.17 4660VO Board 1800Dip Board 3.50Track Cutter 135p100 Pins 49pVeroblock 3 95

Vero WiringPen Spool 3.35Spare Spool 75PCombs 611

PCBMATERIALS

FERRICCHLORIDE

Quick dissolvingpellets i wrth1 litre water) 1.69

Top quality on'tthrow theseD batterms way theycharge up lo 1,000times,HP2 (1.2AH) 2.10HP2 (4411) 4.75HP71 WAH1 lipHP1111.2AH1 2.76PP3 4.96ChargersTYPE HAdjustable to 6of any HP lopeabove 615.59TYPE MAs above butcharges 4AHbatteriesfaster E25.95TYPE PPP3 B.50TYPE A1107 !Up to 4 ata tirnel 05.85

5 6

ANTE%SOLDERINGIRONSC240115WI 4.59025125W1 4.98Iron wand 1.66C240 Element 1.99X25 Element 206Bits C240No. 2 ISmall1 650No 3 Wed/ 660No. 6 Micro) 660Bits 025No.50 (Small) 650No.51 Wed/ 85pNo.52 ILgel 95pSOLDER 12Spm18 swg 2.9522 six.) 310

PLUGSSOCKETS

ETCH RESISTTRANSFERS

1 Thin lines2 Thick lines3 Thin bends4 Thick bends5. DIL pads6. Transistor pads7. Dols holes8. 0.1" edge cons

9 1,:'"=,of

above 35p

ELECTROLYTICSMainly Matsushita

(Panasonic) EtSiemens

AXIALS 'Wireseach ends

ATEcl V47 63 Bp47 100 9p47 350 30P1 63 80

1 100 9P1 500 40p12 75 Bp2 1 63 9p

GRADE ONEGLASS PCBSi gle S'Oed178. 240mm 95p020 . 195mm

130p420 245mm

1950DALO ETCHRESIST PEN

spa, no 90p

PHOTOSENSITIVE PCB1st Class EpoxyGlass. For betterresults than spraying Expose to UV

'Er Connectors25 WaySolderMale 160Femal6 2.09

PCB Wire -WrapMale 1.60Female 2.09Covers £100

Phono PlugsBib R I GrnWht nr Yellow 15pLine SkIs 1511

Chas Skt 120pDuel 30pQuad 40p

TRANSISTORS

Britain's largestretail selection.Asmall sample ofur vast stocks

25930 24259300 34),261893 30p262102 39p151217 39p252218 33p252218A 25p252219 27P2522190 260252220 22p2N2221 22p252221A 23p252222 24p2522224 25p252221 2.602522230 4.15252368 25p252369 19p2623694 16p2529044 270

252905 242529054 29p252906 25p252906A 30p2N2907 24252907A 20p252920 3.472N2923 25p252924 15p2N2925 150252926 10p253053 27p253054 56p253055 60p2143055H 120o253250 36p253251 36p253439 980253440 80p253441 1 252N3442 1 35

2613442RCA 185253445 4 BO

2N3446 6092N3447 5.72253448 8.58253468 1.00253512 1.06253553 2.30

2536380 67p263702 10p2N3703 10p253704 100253705 10p253706 10p253707 10p253708 10p2N3709 10p2N3710 10p253711 10p253712 2.00253713 1.38253714 2 98253715 3.31253716 360253773 1 99253819 26P253820 38p253821 1 842N3822 90p253823 45p253824 1 702N3866 900253903 150

253904 15p253905 15p253906 1511

254030 66p254031 55p254032 65p254036 580254037 43p254240 3002N4347 1262N440) 15p254401 27p254402 30P254403 30p254409 360264410 42o264427 79p264870 80p264871 55p254888 92p254901 1 692N4902 3.52254903 3 20254904 275264905 325254906 342264907 3.X7254908 3.70264909 290254918 95p254919 1.28254920 1.30254921 56P254922 69p254923 99p2N5086 36p2515087 3911255088 37p2745089 37p255190 68o255191 70o2N5193 90p255194 79p255245 37p265246 40p265247 45p255248 46P255249 48p2N5266 2.882N5293 9811

265294 1 28255295 1 37255401 35p255415 1 10255316 154265447 16p265448 19p255449 21p255450 23p255451 250255457 29p255458 29p255459 29p2N5460 72p265551 370265884 5 95765884 595256121 540256121 56p256123 59p256124 56p256125 5902N6126 71p256129 09p256130 93p256131 98p256132 83p256133 1 14256134 1 36256253 1 45256254 1 552SC1306 95p2502078 1 1525349 35025J50 3 7525382 429250134 350250135 3 75250226 4.2935128 1 1235140 2 3735200 6 9335201 2 9840360 60p40361 67p40362 67040363 22240405 13940407 75p40408 15840410 180

40411 18640412 90p40673 830401322 1.8010871 1911

40872 8917AC125 350AC126 2511AC127 250AC128 25pAC132 39pAC141K 28pAC1420 280AC151 51pAC152 45pAC153 550AC1531 64pAC176 27pAC176K 37pAC187 250AC187K 28pAC188 2511AC1880 40pAF239 55pAF240 100AL102 149AU110 2.20AU113 3.67BC107 10pBC107A 120

BC107B 120BC108 lop

801080 12p13010813 12pBC108C 14p80109 10p13010% 12p801090 12pBC140 29p80141 37pBC142 29PBC143 34p8C147 10p801470 10p0014713 10pBC 147C 20pBC148 10pBC 1484 12211

801488BC148C 13pBC149 1011

8C14913 I2P801490 13P00152 35PBC153 23pBC154 27pBCI57 1111

BC1570 12pBC1578 13pBC158 10pBC158A 12pBC158B 13p80159 11p801590 12p0015913 13pBC 159C 18pBC 160 Ile8C161 400BC167 100BC1674 100B C1678 13pBC168 10p8016813 10pBC168C 10p0C169 10pEIC16913 10p801690 10P130177 16pBC177A 25p8C1778 260BCI78 1608C1780 24P13C1788 2598C179 201,BC179A 25pBC 1978 25pBC179C 27pBC182 10p801820 12p8018213 13pBC182L 10pBC182LA 13pBC18.218 14pBC183 lOpBC183A IlpBC 1838 12pBC183C 13pBC1831 10p8018310 130scums 130BC183LC 14080184 10pBC184B 12pBCI84C 13pBC1841 10pBC194113 I3P8C184LC 14p80186 24pBCI87 24pBC212 10pBC212A 12pBC212B 13P13C2121 10pBC21214 130BC21218 100EIC213 10p8C2134 lip1302130 12pBC213C 1330

BC213L 100BC213LA 13pBC213LB 13pBC213LC lopBC214 10pBC214B 12p13C2140 13pEIC2141 10pBC214LB 13pBC214LC 14p

I0p802370 16P002370 17p002370 18PBC238 14p802380 15pB C2388 16pBC2ISC 17pBC239 15p8C239A 16pBC239B lipBC239C 18oBC300 4508C301 44p

13C3132 43pBC303 47pBC327 140BC328 140BC337 15080338 150130440 32pBC441 33p130460 32o130461 330BC516 40pBC517 40p00540 /3p

B05474 140805178 14pBC548 12pBC5484 130BC548B 140BC548C 15p00549 13p805498 14pEIC549C 15pBC550 30pBC550C 33pBC557 15pBC557A 16p1305578 16pBC558 14030558A 150BC55813 16pBC558C 17pBC559 15pEI055913 16p805590 17pBC560 32p80560C 34p8C850 45pBC65I 46pBCY70 16pBCY71 16pBCY72 19pBDI31 44p80132 44pB D135 40p80136 40pBDI37 42pBD138 39p80139 399130140 39p80237 98p00238 960BD239A 57p802390 64pBD240A 59pB0240C 7311

80241A 61p802410 67p802420 65pBE/242C 70p002430 72pEI02430 85p802440 82p802440 1 00002450 1.14802450 1 30802460 1 20602460 1 50002490 2 00602490 2 31002500 211BD250C 206130437 88p130438 88p60439 90060440 91p130441 91p80442 93p130529 1.20BD530 13000535 75o130536 75p130537 80pBD538 80p130539 809805390 1.1000540 1154*

805401 1.20130675 72080676 77p80677 780BD678 83p130711 13280712 1 3280014 1 30110)(18 159813032 347BDY54 170BDY55 1.75BOY56 1.80BDY57 5.2500158 6.158E194 12p8E195 12P00196 12P8E197 12pBF198 15p8E199 15pBF200 149BF224J 320ElF2253 3511

8E240 3890F241 38pBF244A 35pBF244B9F245A 30pBF245E1 51pFiF246 52p802460 39p802460 53001247A 54pBF247B SSo13E254 39P8E255 42pBF2564 3511

130256E1BF256C 820ElF257 3011

8E258 32.00025981457 46pBF458 58p8E459 52p80469 85p00470 85pBFR39 2998FR40 25p131041 259BFR79 250131880 250BER81 25PBER90 211ElF528 2 958E561 1508E598 170BF X29 2fipB F 030 27p00050 23pBEY51 23pBEY52 23pBEY53 31pBSX19 24pBSX20 24p05021 40P00104 22280105 170001100 295130109 32905.126 147BU204 225130105 115O 6206 189911708 1 98011226 3258113265 235RU406 1 4501)401 1 4581408 1 3582500 2 95BUY18S 3%

CRICKLEWOOD ELECTRONICS LTD.40 Cricklewlood Broadway, London NW2 3ET. Tel. 01452 0161. Tlx. 914977.

Here's a selection from our vast stocks. Full price list f ee on request Orders by 'phone quotingcredit card no. or by mail order. Callers welcome. All products first grade franchised source.

All In -stock items despatched same day. Official orders welcome from Govt. Depts, schools, etc.Please add 600 p&p t- 15% VAT. Overseas orders no VAT but allow £2.00 min p&p.

Quantity discounts negotrahle

1430 595J300 48pJ310 53p94 802 39M1900M3901 110MJ1000 2.50MJ1001 3.00M31800 160MJ2500 /19MJ2501 2.25MJ2955 1.00MJ3000 2.19MJ3001 2.2551)4502 19951)1 5003 4.8551)15004 855M)15015 2.45Mi15016 3.34MJE340 539MJE350 1 50MJE2955 49pMJE3055 69pMPS405 239MPSA06 250MPSAIO 290MPSA12 29pMPSA13 48pMPSA14 46pMPSA16 30pMPSA18 65pMPSA20 48pMPSA42 49pMPSA43 49pMPSA55 280MPSA56 300MPSA65 400MPSA66 470MPSA70 45pMPSA92 390MPSA93 390MPS LO1 020MPS L51 48p

MMPPSSUL/04C" "p1.32MPS 1105 550MPS UO6 56pM

MPS U56 59pMPSU57 1.200020 2.30

°C13C225250

0 1700029 2150C354 23:

0044 520OC70 50p0071 50p

50p

000112P a38292 A29 '325 PPP

TIP3IC 38pTIP300 35pTIP3OC 38p

I -10'31A 3311I3C 390TIP32A 350TIP32C 42p

TnIPP3333CA 5785pp

TIP34A 74pTIP34C 81/pTIP35A 1.09TIP35C 1.29TIP36A 1.29TIP36C 1 39TT,IPp4411cA 49P

Try,,,,P444922c490575pA.

TIPS° 1.40TIP53 1.57IPS4 168

TIP110 74pTIP112 90p

TTT LPP111201175 96ripp

TIP122TIP 125TIP127TIP130 9'1ppTIP132 93oTIP135 99pTIP137 99pT1P140

1TIP 142 15044TIP145 1.15TIpP,16427 1.15

OTIP2955 urpTIP3055 7096543 409115880 62oVNIOKM 60oVN46AF 8440

VN66AF 850ZT0I07 10pZTX106 10pZTX109 10pZTX300 13pITX301 15pITX302 15pZTX303 130ZTX304 160Z210331107 1325pp

ZTX312 350ZTX313 36pITX314 24411

U27;333020 335N1,7

2T0341 290270450 390270500 14p27X501 14p214502 140ZTX503 17pZTX504 24pIT)(510 34pITX530 24p27 0531 25921)/(650 1511

DIODES15340 30p15821 70p15823 92p15914 Bp15916 10p154001 4p150002 404p154003 5 `hp154004 6 kkp154005 6p154006 8'hp154007 7p154009 20p154148 6p15415(1 18P154448 22p155400 12p155401 130155402 14p155403 15p155404 1811

155406 18p155407 19p155408 20o155024 52p1544 10pBAIO2 25pBA115 25000133 40pBA 138 30p130142 20pBA155 15pBA156 380BA157 250134158 30pBA159 32pBA182 40P00201 189BA202 26pBA316 2Sp65317 25080316 30p80010 16p84019 15p90020 15PBAX13 10PBAX16 11pBY126 20p80127 22pBY134 52pBY 1W 126130206 36pBY207 360BY223 1 5600297 48pBY299 550MZ2361 1 BO

0447 20p0490 10p0091 10p0095 20p00200 213p

00202 20p

TRY US NOW - WE'VE GOT WHAT YOU NEED.

50414001 lOpS01319301 559

6 amp typeSquare with hole

PW0111001 500PW0212001 7119PVV0414001 85pPW0616001 90P

25 amp typeMetal clad withbole

001 11001 2.20002 12001 23000414001 2.80K0616001 3.40

SCRs TRIACSMACS

THYRISTORS4 8812 AmpsTexas 10220

Suffice. A - 1000B - 200VC-3005D 4130VM 600V

TIC106A 46pT1C1068 47pTICIO6C 4111/

4A TICIO6DTIC1043M

TIC1164 66p11011613 68p

134 TIC116C 71pTI01160 730TIC116M 80p7101260 72pTIC126B 720

2A 0101260 7307101260 77pTIC126M 9511

TRIACSTexas 4000

00220 CaseTIC206014.11) 650TIC225D1641 74p7IC22601801 88011023601120I

1.16TIC2460116A1

1/2TIC253D120A1

1.9011026301250I

2.11

DIACS80100 40pST2 25p

LEDsR = RadG - Green

= YellowLarge diffused

051) 9p 7pG5D 15p 12p550 150 12pSmall diffusedR20 511 511

12p 1011

YID 12o lOpMicro 0 1

RID 25p 22PGI D 27p 25pYID 27p 25pLarge clearR5C 12p 10pG5C 17p 13pY5C 17p 13pSuper bright higheft icrencyLarge 1100times brighter IR5U 38p 29pGSU 42p 34Y5U 42p 34pRectangularStackables LEDsR6L 17pG6L 180Y6L 190

LINEAR ICs

ZENER DIODES

400 500mWE24 Series

2 4 47V 7p

1 3 WattE24 Series3 3 82V 149

BRIDGERECT01ERS

(Ply shown inbrackets)

1', amp type

W01111301 24W0212001 26pW0414001 21p0008 18001 414

2 a.np typeSquare wall hole

S0111601 37pS0211001 40p

AY1 5050 95pAY3 8910 5.46AY] 8912 5.59003048 2.99CA3059 2.80CA309040 370CA3130E 87pCA31331 1 80CA31406 39pCA3140T 950HAI366W 2.40001388 2.54IC17106 750IC17107 9 751CL7611 97p1C176130 1 95ICL8038 2951CL7555 80pICL7556 1 50LC7120 320LC7130 320LC7137 3851E347 1401E351 47pLF353 92pL F355 83pL F356 92oLF357 109103% 459LM335Z 1.19LM348N 62pLM349N 116LM350K 460LM379S 450L M380514 7501M38058 150L6138105 2.26LM381N 140LM31325 1 12LM383T 340LM3134N 1 40LM356 gapL638813 243LM391560 170LM391580 1.93LM723CH 1 21LM723CN eopLM725CH 340LM725C5 3 19LM733 690LM741CH 96pLM741CN 15pLM747CN sgpLM748CH 1 00LM748C5 350LM1871 4391M1872 438LM1886 7041M1889 3 77LM29075 2 75LM2907N8 260LM29175 189LM29175 1891.543900 49p18.43911 170LM3914 200LM3915 200LM3916 2.50LM13600 1.100M335 720NE5315 1,365E5435 250NE54415 100NE555 16pNE556 450NE558 189NE560 325NE565 118NE566 149NE567 1.37NE570 3.76NE571 8.75NE5534A 95p

011024 4/5PL1034 12.75RC4136 5911

T130500 2171005000 111TBA5I0 1%TBA5100 3.06TBA520 2.5711105200 2.76180530 155TBA5300 216TBA500 /72TBA54013 2.74TBA550 3.257I345500 127TBA560C 2.87TBA570 /37TI345700 2.48

74156 40p74157 30074159 75p74160 40p74161 40p74162 40P74163 40p74164 40p74165 40p70166 48p70170 1 1774172 25074173 48o74174 54p74175 49p74176 39p74177 45074178 68p

TCA910 /19 74190 40pTCA940 1.99 741131 1 150001002 3.39 74182 56oTDA1003 194 74184 9007041004 2.87 74185. 90oTO41005 3.94 70186 4 6970010104 2.25 70188 2.50TDA1022 495 74190 45oTDA 1024 1.19 74191 450TDA2610 3.90 74192 45pTDA26114 2.50 74193 450U44170 1.59 74194 4001104180 1.69 74195 40pULN2003 85p 74196 40pUPC575C2 2.50 74197 414/UPC1156 /76 74198 77p002206 2.92 74199 27p75414 79p 74221 53p25419Z51034

1 901.90 7415 TIT

251040 075

74 ,L

7400 11p7401 11p7402 1107403 1297404 12p7405 15p7406 16p7407 1607408 14p7409 14p7410 15p7411 1697412 14p7413 16p7414 17p7416 I7p7417 17p7420 1597421 20p7422 20p7423 20p7425 18p7426 lap7427 lag7428 lop7430 1407432 17p7433 21p7437 19p7438 19p7440 1507441 65p7442 27p7443 8507444 65p7445 46p7446 5057447 35p7448 15117450 1557451 15p7453 15p7454 1407460 15p7470 313p7472 26p7473 23p7474 1807475 22p7476 24p7480 40o7481 1.197082 63p7483 3SP7484 63127085 60117486 11Ip7489 1.707490 21117491 3507492 2597493 3407494 2407495 34p7496 34p7497 B5p

74100 80p74104 501174105 55P74107 20p74107 20p74109 25p74110 29P74116 50p74118 S3p70119' 57p74120 59P74121 25p74122 30p74123 341374125 30p74126 29074128 35p74132 29P74136 27o74101 55p74142 17574143 1 9574144 1 9574145 38P74147 89074148 55p74150 49p74151 35074153 35o74154 49p74155 40o

741530 1 1p741501 Ilp741502 lip741503 12p741504 12p741.505 12p74LSO8 12p741510 12p741011 12p741512 12p74LS 13 19074L514 220741515 140741520 12074LS21 12p74LS22 120741.527 12p741028 I4p741.530 12p74L532 13p741533 1111

741537 I4p741.538 14p741540 11p741.542 280741547 3517741551 140741550 14o741955 140741573 180741574 14741 575 18o741576 180741578 I8p741580 120741083 33o741585 39p741586 16p741590 22p741592 2511

741593 24p741595 36p741596 50p741_5107 20p7415109 23p74LS112 2007415113 220

' 7415114 22P741.5122 25P74L5123 3407415124 alp74LSI25 24p2415126 250731513/ 3307415136 24p7415138 24p7415139 27p7415145 70P7415147 99074LS148 69p745151 30p7415153 39p741 5154 79p7415155 29p7415156 36p7415157 2707415158 28p74L5160 32p741.5161 35p741 5162 35P7415163 35P1415164 4007415165 50p741.5168 11407415169 5507415170 70P7415173 55p7415174 39p70.0175 3907415181 88p7415183 1X17415190 36p7415191 3607415192 3607415193 37p7415190 3207415195 32p7415196 45p7415197 4807415221 50p0415240 55P7415201 56p7415242 55p7415243 55p741 5244 55p7415245 70p74L5247 50p14L5208 56p7415249 5507415251 30p

7415253 320741.5257 29p7415258 33p7415259 55p741_6261 99p7415266 18p7415273 5307415275 1257415279 30p7415280 95p7415283 43p7415289 4 707415290 45p741E293 40p7415295 75p7415298 79p7415299 1.557415323 165741E324 1.457415325 2.%74LS326 2.307415327 2107415347 95p7415348 1114

7415352 79p741.5353 79p741 5362 7.257415365 29p7415366 29p7415367 29p7415368 29p7415373 590741 5378 58P7410386 1.14741 0390 06o7415383 41p741 5395 89p741 5396 1.9074153% 2.707415399 1.597415445 947415490 2.20741E540 1.607416541 99p7415640 169741S641 169

EMUS

4000 10p4001 10p4002 11p4006 49p4037 15p400E1 32p4009 24p4010 24p4011 10p4017 15p4013 20114014 4504015 39p4016 20p4017 np4018 44p4019 2504010 44p4021 39p4027 39p4023 12p4024 32p4025 12p4026 77p4027 20p4028 37p4029 43p4030 1404031 1.194032 19304033 1.204034 1294035 59p4036 2494037 13)4038 99P4040 40p4041 40p4042 o4043 43944044 Ile4045 99P4046 4400047 39p4048 3904049 22p4050 23p4051 444052 49p4053 494,4054 0394055 8304056 89p4059 4 354060 42p4063 79p4066 32p4067 /224068 1404069 13p4070 13p4071 13p4072 13p4073 13p4075 13p4076 44p4077 13p4078 13p4081 12p4082 12p4085 49p4086 53p4089 1 204093 1004094 69p4095 75P4096 70p4090 2.884t)98 74p4()99 9094502 50P4503 29114507 33p0508 1.194510 45114511 40p4512 3911

4514 1 104515 1.104516 50p

0518 340519 29P4520 45P4521 9004526 5964527 59p4528 4001537 69p4534 4294536 2 594538 6504539 9904543 65p4553 2251555 35p4556 3504560 1404506 1 404560 1 591584 39p4585 79p

LOGIC

CPU's11302 70026500 11.996502 1476800 2.256802 2 456809 6 248935 3.1913060 10 9080800 2.3080850 149SCMP1 17.067800 2.%

MEMORIES

2114 1200ns, 93p2532 3602564 11 952764 7.752708 225271615V1 2.1041161200ns1 77p4118 3 1254164 1955101 145Onsl 1.895204 7.506116 3 856514 3.306810 1157489 4X14189 000

7415289 3.257415188 2.257415287 3057415288 2.25

MISC LOGIC ICs4000804 3.95ADC0816 14.90ADC0817 10.06405 2376 5 %1551671 20801651771 2000110251310 6.99R02513UC 7.50SAA5000 300SAA5010 710SAA5012 710SAA5020 5.505005030 9.00SAA5040 15 00SAA5041 15 00SAA5050 850SAA5052 850TMS6011 3658126 95p8T28 1208795 85p8797 850811595 90p811596 120811597 900811598 .1 206522 3196532 6958154 94Z8155 3508212 1 108216 99p8224 1058226 2 478228 220ZEIOACTC 2.6028000007 5.50ZBOADMA 6.70Z90APIO 26976425E8 3.39

VOLTAGE REDS

- Positive100mA

78105A 26p781120 260781150 26P781240 300

1 Amp 7022078050 39p/8127 39p78157 39p78247 39p

- Negative100inA 1092

791.05 59p79111 59p79115 59p

1 Amp 7022009051 44p79127 44p19151 44p79241 44p

210 SOCKET

24 Pin 435

SWITCHES

Toggles (MindSPS7 49pSPOT 55p[VD' 69p(0301 C 00 85pVDT 2 75


Careers in Electronics

LAREERS INELECTRONICS

Charles Harvey

It takes study, but not a higher degree, towork in the high -flying industry of theeighties.ALTHOUGH electronics is now taughtas a subject in many schools, the realcourses of electronic education do notproperly begin until after leaving school.And then you will find there are aconfusingly large number of coursesavailable! Before deciding which one tochoose, then, you should ask yourselftwo very important questions:

What qualifications am I likely to haveafter leaving school?

Do I want to be a full time student orwould it be better to work, and study parttime?The importance of the first question isfairly obvious: the course you will beable to take will depend largely on thequalifications, if any, that you carryaway from the school years. But even ifyou leave with very few formal grades,all is not lost.

Entry to one of the ITECs (InformationTechnology Centres), set up by thegovernment to teach young people theessentials of electronics and micro -computing, requires no formalqualifications - just an interest andwillingness to learn. The courses last upto a year and provide, at the least, abasic understanding of the subject -what you do with it then is up to you!

If you want to find out about ITECs inyour area, the information is availablefrom your local Careers Office, who willhave all the details at their fingertips -if there is an ITEC nearby.

Young people who are leaving schoolbefore reaching the grand old age of 18should also consider the government'sYouth Training Scheme. This startsofficially in September 1983, but someschemes are being set up as early asApril. They will offer the equivalent of atleast three months full-time training,

and up to nine months of relevant workexperience; for example, a person mightspend a quarter of his or her time at alocal college or industrial trainingcentre and the remainder working withan electronics firm in the neighbour-hood. Once more, your future aftercompleting the course is left in your ownhands.

The Youth Training Schemeorganisers hope that they have learnedfrom the experience gained on theYouth Opportunities Programme, andthat the new scheme will offer betterquality training; however it is new, sowe will just have to wait and see if it issuccessful.

Gilt Edged CertificatesThose who leave school with a reason-able range of CSEs (or who pass collegeselection, in Scotland) could normallyaim for a course leading to a City andGuilds Certificate.

The City and Guilds of LondonInstitute, to give it its full title, is anorganisation over 100 years old thatawards a qualification to crafts men andwomen in many different industries -catering, building, engineering andneedle trades, to mention a few. Theircertificates in electronics can be takenfull time at many colleges, though mostpeople attend part time on day or blockrelease from a job.

This is where the answer to thesecond question is needed: full timeeducation is expensive (as every parentknows), but finding an employer whowill offer you day or block release fromthe job will depend on the employmentsituation in your area. Given thenational employment situation, this islikely to be difficult.



There is no quick and easy solution tothe problem, either, unless full timestudy is a realistic option. Financialassistance is available for somecourses, and a few of the options arebriefly summarised in Table 1. Manypeople would prefer employment ofany kind, even if not in the electronicsindustry, to no employment at all - butit's worth considering that any job in anelectronics industry (even if itssweeping the floor!) could allow you toundertake a City and Guilds course,perhaps leading to a brighter future. Ofcourse the educational qualificationsmust be met, and entry into thebusiness in this way would be mostunusual - but always worth a try if allelse fails!

The City and Guilds qualification mostrelevant to electronics work is the '224Certificate'. All those who take thiscourse do a 'Part I', which takes about300 college hours and covers thefundamental knowledge needed (safety,electronic units and systems, trans-mission, wave forms, electrical suppliesand circuits, resistance, magnetism andelectrostatics, capacitance andinductance, heat, sound and light, theuse of tools and instruments, and aheaped helping of maths, includingbinary arithmetic). Part II usually takesabout 600 hours and contains coresubjects which are taken by allstudents, but then allows the option ofspecialisation in either Radio/TV orIndustrial Electronics. It is also possibleto carry on to the Advanced Level (PartIII), a specialist option covering TV ingreater depth, including video recordingsystems, information technology,AM/FM radio and audio systems,microcomputer systems, electronicmeasurement and control systems.

Electronic work is also covered in twoother City and Guilds Certificates; the'225', Maintenance Craft Studies inInstrumentation and Control covers theinstallation, maintenance and repair ofinstruments used in industrial plants,while Electronic Craft Studies ('232') isfor those working in industry andbuilding services, and coversapplications of heavy duty electricalengineering as well.

TEChnician TrainingAs with City and Guilds, part-time studyon release from full-time employment isthe most common way to gain TEC(Technical Education Council) orSCOTEC (Scottish Technical EducationCouncil) qualifications. The minimumentry level for a TEC course is gradethree CSEs in English, Maths and ascience subject (or, in Scotland, beingable to pass college selection), thoughsome may demand higher entry qualifi-cations. Relevant O-level/O-gradepasses in, for example, Maths, Physicsor English, usually permit exemptionsfrom Level 1 courses, proceedingdirectly to Level 2 and finishing thecourse more quickly.

TEC/SCOTEC Diplomas are usuallytaken by full-time study and reach thesame level, but in a wider range ofsubjects. Generally if you start at level 1,a TEC/SCOTEC Certificate takes three

years part-time, and a Diploma takestwo years full time - but there areexceptions in both cases.

Older readers may remember theOrdinary National Certificate andDiploma courses (ONC and OND); thesehave now been superseded by theTEC/SCOTEC qualifications and,broadly but not exactly, they are themodern equivalents.

Just as TEC/SCOTEC Certificate andDiploma have replaced the oldONC/OND, so the old Higher NationalCertificate and Diploma courses(HNC/HND) have been replaced by theTEC/SCOTEC Higher Certificate andDiploma. The usual entry requirementsfor the higher courses are either aTEC/SCOTEC Certificate of Diplomapass, or an A -level pass together withan attempt at another relevant A -levelsubject such as Maths, Physics,Electronic Systems etc; two 'highers' ora SCOTEC Certificate or Diploma areusually required in Scotland.

Degrees Of LearningAgain, the usual way of completing a

Higher Certificate is by part-time study,while the Higher Diploma is usuallytaken full-time.

One feature of these qualifications isthat they are made up of self-containedunits which are devised by the collegesthemselves, though approved by theTechnical Education Council. As aresult, there are often differencesbetween the courses run by differentcolleges. The TEC recommends that acourse should contain some maths,physical science and industrial skills,plus electronic systems, digitaltechniques, general and communica-tion studies; the range of specialistoptions usually cover radio, TV and tele-communications subjects. At the higherlevels, there are further specialist unitsdealing in advanced radio/TV, radar,measurement techniques and faultdiagnosis, etc. There is even morediversity at the upper levels because theTEC does not lay down such firm guide-lines, and colleges are free to developcourses appropriate to the needs of localindustry.

For those with two or three goodA -levels (or three or four H -levels inScotland), there are degree courses atUniversities, Polytechnics and ScottishCentral Institutions. In England andWales, degree courses last three yearsnormally (four years in Scotland) but'sandwich' courses, with industrialexperience included as part of thedegree, will last four years.

For those who do well at degree level- and this means either a First orSecond class degree - there is achance for higher scholastic honours,usually a Master of Science (MSc) orDoctor of Philosophy (PhD) degree.However, competition for the limitednumber of grants supporting higherdegree study is limited, so that even agood degree is not sufficient, alone, toguarantee grant approval.

Another question which every schoolleaver - indeed, every person intraining - will want answered is: what



Table 1

Course

ITECsYouth Training Scheme

Full time City & Guildsand TEC courses

Full time HigherTEC Certs/DipsDegree

Grants & Finance

Government allowance, currently £25.00 pw and fares in exess of £4.00.

Free tuition if under 18. Only a few authorities (eg Sheffield, ILEA) pay maintenance grants.Fees are payable for over 18s. You may be able to get a discretionary grant from your localauthority but it depends where you live. Ask the advice of your local Careers Service, or yourlocal authority's grants department.

You can usually get a mandatory grant from your local authority (Scottish Education Dept.in Scotland) regardless of where you live. This covers tuition and is supposed to cover livingexpenses, though most students find it hard to live on! It is "means tested" - how much youget depends on how much your parents earn; they are expected to make up the difference.There are different rules for mature students.

Table 2

ENTRY

No formalqualificationsrequired

COURSE

ITEC

No formal New "Youthqualifications Training"

Sometimes no City & Guildsformal qualifica- Cert.tions butgenerally CSEs

CollegeSelection(Scotland) orgrade three CSEs

TEC/SCOTECCert./Dip.

TEC/SCOTEC TEC/SCOTECCert./Dip. Atleast one A -levelpass or twoHighers (Scotland)

Two/three good DegreeA -levelsthree/fourHighers

Higher Cert./Dip.

AT

ITEC

COMMENTS

Practical experience in micro com-puting and electronics.

Further education Starts Sept '83. Exact details still un-certain but probably includes at least3 months full training plus relevantwork experience.

Further educa-College

FE College

FE College orPolytechnic

Polytechnic orUniversity orCentral Inst. or,occasionally,FE Colleges.

Full time course (usually takes twoyears) or part time, day or blockrelease, usually lasting three years forthose in employment; leads to craftcertificates.

Full time course, usually two -threeyears, often taken part time by thosein employment.

Full time course usually lasting twoyears. Often taken part time by thosein employment.

Three years for full time course, fouryears for sandwich course; four yearsin Scotland.

POSSIBLE JOBS

Hi-fi servicing,electronicassembly.

Not known yet.

Hifi servicing, alarmsystems installa-tion, etc.

Radio/VTRtechnician.

Computer serviceengineer; control &instrumentationengineer.

Design engineer.

sort of job will my training lead to?

Jobs For The BoysAn attempt to answer this question, ingeneral terms, is made in Table 2,which summarises the various coursesmentioned in this article and describes,very roughly, the type of employmentwhich could result. Naturally, whether ajob is actually available for you dependson the competition, both locally andnationally; generally electronicsgraduates and holders of HigherTEC/SCOTEC qualifications will dobetter in the hunt for jobs than thosewithout. Below this level the number ofjobs available is not so great, comparedwith the number of people seekingemployment, so the competition ismuch tougher.

14

Don't Need No EducationYou might, by now, have the impressionfrom all this verbage that the only wayinto employment in electronics isthrough a more -or -less specialistcourse of training. However manyemployers look rather for a good all-round education in relevant subjects.Some prefer to recruit young peoplewith, say, four 0 -levels or 0 -grades,including Maths, Physics and English;or with Math and Physics at A -level orhigher levels in Scotland. As mentionedearlier, it is now possible to studyelectronics at 0- or A -level in manyschools, in courses including electronicsystems and microcomputers, and anystudy at school will naturally beadvantageous when you later come toselect a career in electronics. HE


THE NEN WHO INt.)CLEVER- F.. -4 jui---;h1 ToIN 0 RTT H- I -T SFIND 4- T INES MORE

:E.

'CET RE DUttiE FOR rFic.1

Richard Altwasser and StevenVickers are the men who invented theJupiter Ace.

After years of designing micro-computers that use BASIC (both menplayed a major role in creating theZX Spectrum), they abandoned it infavour of FORTH.

FORTH is just as easy to learnas BASIC. Yet it's a faster, morecompact and more structuredlanguage that educationalistsand professional programmersalike prefer.

So the Jupiter Ace is the only micro-computer you can buy that is designed aroundFORTH.

Using it, there's little fear of accidentally'crashing' programs halfway through and havingto start all over again (a common fault withBASIC). The Jupiter Ace's comprehensive errorchecking sees to that.

The Jupiter Ace has a full-size keyboard,high resolution graphics, sound, floating pointarithmetic, a fast, reliable cassette interface,3K of RAM and a full 12 month warranty.

You get all that for £89.95. Plus a mainsadaptor, all the leads needed to connect mostcassette recorders and T.V.'s, a softwarecatalogue (35 cassettes available, soon to be 50),the Jupiter Ace manual and a free demonstrationcassette of 5 programs

The Jupiter Ace manual is a completeintroduction to personal computing and asimple -to -follow course in FORTH, from firstprinciples to confident programming.

Plug -on 16K and 48K memory expansionsare also available, at very competitive prices.(There'll be a plug -on printer interface availablesoon, too.)

It'll take you no time at all to realise howclever Richard and Steven were to design theJupiter Ace around FORTH. And even less time torealise what a silly price £89.95 is to charge for it.

ED E 1.. ERE

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Technical InformationHardware180A; 8K ROM; 3K RAM.

Keyboard40 moving keys; auto repeat; Caps Lock.

ScreenMemory mapped 32 col x 24 line flicker- freedisplay upper and lower case ascii characters.

GraphicsHigh resolution 256 x 192 pixel user definedcharacters.

SoundInternal loudspeaker may be programmed forentire audio spectrum.

CassettePrograms and data in compact dictionary formatmay be saved, verified, loaded and merged. Alltape files are named. Running at 1500 baud.

Expansion PortContains D.C. power rails and full Z80 Address,data and control signals. Can connect extramemory peripherals.

EditorAllows complete editing and listing of compiledprograms.

Please send cheque/postal order to:Jupiter Cantab, 22 Foxhollow, Bar Hill,Cambridge CB3 8EP.

Jupiter ACEPlease send me Jupiter Ace microcomputers @ £89.95 (+ £3.95 p. & p.)

Tick here if you require VAT receipt

Name

Address

010 01 83

Available for immediate delivery. Allow 14 days for p. & p. U.K. price only (export price on request).


G ETBIG POINE,

ir ModularAmplifiers

the third generationDue to continous improvements in components and design I LPnow launch the largest and most advanced generation ofmodules ever.

WE'RE INSTRUMENTALIN MAKING A LOT

OF POWERIn keeping with I LP's tradition of entirely self-contained modulesfeaturing, integral heatsinks, no external components and only 5connections required, the range has been optimized for efficiency,flexibility, reliability, easy usage, outstanding performance, valuefor money.With over 10 years experience in audio amplifier technology I LPare recognised as world leaders.

BIPOLAR MODULES

ModuleNumber

OutputPowerwattsrms

LoadImpedance

_n_

DISTORTIONT.H.D. I.M.D.Typ at 60Hz/1KHz 7KH: 4.1

SupplyVoltage

TYP

Sizemm

WTgm

Priceinc.

VAT

I IY 10 15 4.8 0.015% <0.006% 1 18 76 x 68 x 40 240 18.40110611 30 4-8 0.015% <0.006% ± 25 76 x 68 x 40 240 £9.551111080l 30 30 4-8 0.015% <0.006% t 25 120 x 78 x 40 420 118.69110124 6 0 4 0.01% <0.006% i 26 120 x 78 x 40 410 120.75110128 60 8 0.01% <0.006% s 35 120 x 78 x 40 410 £20.75110244 120 4 0.01% <0.006% i 35 120 x 78 x 50 520 125.47111248 120 8 0.01% <0.006% 3 50 120 x 78 x 50 520 125.471tY364 180 4 0.01% <0.006% t 45 120 x 78 x 100 1030 138.411.1Y3611 1HO 8 0.01% <0.1)06% 260 120x 78 x 100 1030 138.41

Protections. Full load line. Slew Rate: 15v/ps. Risetim, 5ps. S/N ratio: 100db.Frequency response -3dB) 15H - 50KHz. Input sensitivity'.500mV rms.Input Impedance' 100K fl . Damping factor 100Hr >400.

PRE -AMP SYSTEMS

ModuleNumber

Module Functions CurrentRequired

Price inc.VAT

IIVI; Mono pre amp Mic/Mag. Cartridge/Tuner/Tape/Aux Vol/Bass/Treble

10mA C7.60

11'166 Stereo pre amp Mic/Mag. Cartridge/Tuner/Tape/Aux Vol/Bass/Treble/Balance

20mA 114.32

IIY /13 (tome pre amp Two Guitar (Bass Lead) and Mic Separate Volume Bass Treble Mix

20mA 115.36

110 /6 Stereo,pte amp As H Y66 less tone controls 20mA 114.20

Most preamp modules can be driven by the PSU driving the main power amp.A separate PSU 30 is available purely for pre amp modules if required for£5.47 Inc. VAT). Pre -amp and mixing modules in 18 different variations.Piease send for details.Mounting BoardsFor ease of construction we recommend the B6 for modules HY6-HY13 £1.05(inc. VAT) and the 666 for modules HY66-HY78 £1.29 (Inc. VAT).

POWER SUPPLY UNITS Il ncorporating our own toroidal transformers)

ModelNumber

For Use With Price ine.VAT

PSU 21% 1 or 2 HY30 £11.93PSU 415 1 or 2 HY60, 1 x HY6(160, 1st -10124 f13.83P0042% 1 a HY128 E15.90PSU 43% 1 x MOS128 116.70PSU 51% 2 x HY128, 1 x HY244 £17.07

MOSFET MODULES

ModuleNumber

OutputPowerWatts

1.1715.

LoadImpedance

SIDISTORTION

T.H.D. I.M.D.Typ at 60Hz/1KHz 7KHz 4:1

SupplyVoltage

TM:

Sizemm

WTgms

Pricemc.VAT

MOS 128MOS 248MOS 364

60120180

4-84-84

<0.005% <0.006%<0.005% <0.006%<0.005% <0.006%

u 45± 55I. 55

120 x 78 x 40120 x 78 x 80120 x 78 x 100

420850

1025

1-3041130.86L45.54

Protection: Able to cope with complex loads without he need for very specialprotection circuitry (fuses will suffice).

Slew rate: 20v/ps. Rise time: 3ps. S/N ratio: 100dbFrequency response 1-3dB): 15Hz - 100K Hz. Input sensitivity: 500rnV rmsInput impedance: 100K -0- Damping factor. 100Hz >400.

'NEW to ILP' In Car EntertainmentsC15Mono Power Booster Amplifier tel increase the output of your existing car radioOr cassette player to a nominal 15 watts rms.

Very easy to use.

Robust construction. £9.14 (inc. VAT)Mounts anywhere in car.

Automatic stretch on.

Output power maximum 22w peak Into 4I1Frequency response 1-3d81 15Hz to 30KHz, T.H.D. 0.1% at lOw 1K HzS/N ratio (DIN AUDIO) 80dB, Load Impedance 311Input Sensitivity and impedance Iselectable) 700mV rms into 15K II 3V rms into 811Size 95 x 48 x 50mm. Weight 256 gms.

C1515Stereo version of C15.

Size 95 x 40 x 80. Weight 410 gms.

£17.19 (inc. VAT)

ModelNumber

For Usa With Price ineVAT

Pal 52% 2 x fi Y 124 117.07PSU 53X 2 x MOS128 £17.86PSI) 54X 1 x HV248 117.86PSU 55% 1 x MOS248 119.52PSU 71% 2x HY244 £21.75

Please note X in part no. indicates primary voltage Please insert "0" in place ofX for 110V. "1" In place of X for 220V. and "7" in plat of X for 240V.

ModelNumber

For Um With Prim ins.VAT

PSU 72X 2 x I-10248 £22.54PSU 73X 1 x HY364 £22.54PSU 74X 1 x HY368 124.20PSU 75% 2 x MOS248, 1 x MOS368 £24.20

'1


WITH A LOT OFHELP FROM CD ELECa- TRONICS LTD

PROFESSIONAL Hill THAT EVERY ENTHUSIAST

CAN HANOI!UnicaseOver the years I LP has been aware of the need for a completepackaging system for it's products, it has now developed aunique system which meets all the requirements for ease ofassembly, adaptability, ruggedness, modern styling and aboveall price.

Each Unicase kit contains all the hardware required down tothe last nut and bolt to build a complete unit without theneed for any special tools.

Because of I LP's modular approach, "open plan" constructionis used and final assembly of the unit parts forms a compactaesthetic unit. By this method construction can be achieved inunder two hours with little experience of electronic wiringand mechanical assembly.

Hi Fi SeparatesUC1 PRE AMP UNIT: Incorporates the HY78 to provide a"no frills", low distortion, (<0.01%), stereo control unit,providing inputs for magnetic cartridge, tuner, and tape/monitor facilities. This unit provides the heart of the hi fisystem and can be used in conjunction with any of the UPUnicase series of power amps. For ultimate hum rejection theUC1 draws its power from the power amp unit.

POWER AMPS: The UP series feature a clean line front panelincorporating on/off switch and concealed indicator. They aredesigned to compliment the style of the UC1 pre -amp.Performance for each unit which includes the appropriatepower supply, is as specified on the facing page.

Power SlavesOur power slaves, which have numerous uses i.e.instrument, discotheque, sound reinforcement, feature inaddition to the hi fi series, front panel input jack, levelcontrol, and a carrying handle. Providing the smallest,lowest cost, slave on the market in this format.

UNICASES

HIFI SeparatesPrice inc.VAT

UC1 Preamp £29.95UPS X 30 + 30W/4-811 Bipolar Stereo HiFi £54.95UP2X 60W/411 Bipolar Mono HiFi £54.95UP3X 60W/811 Bipolar Mono HiFi £54.95UP4X 120W/411 Bipolar Mono HiFi £74.95UP5X 120W/811 Bipolar Mono HiFi £74.95UP6X 60W/4-811 MOS Mono HIFI £64.95UP7X 120W/4-811 MOS Mono HiFi £84.95

Power SlavesUS1 X 60W/ 4 fl Bipolar Power Slave '£59.95US2X 120W/411 Bipolar Power Slave £79.95US3X 60W/4-811 MOS Power Slave £69.96US4X 120W/4-811 MOS Power Slave £89.95

Please note X in part number denotes mains voltage. Please insert '0' In place ofX for 110V, '1' in place of X for 220V I Europel, and '2' ,n place of X for 240V(U.K.) All units except UC1 incorporate our own toroidal transformers.

TO ORDER USING OUR FREEPOST FACILITYFill in the coupon as shown, or write details on a separate sheet of paper,quoting the name and date of this journal. By sending your order to ouraddress as shown at the bottom of the page opposite, with FREEPOSTclearly shown on the envelope, you need not stamp it. We pay postage foryou. Cheques and money orders must be crossed and made payable to I.L.P.Electronics Ltd. if sending cash, it must be by registered post. To pay C.O.D.please add £1 to TOTAL value of order.

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IL IIPPost to: ILP Electronics Ltd., Freepost 4,

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COMING SOON TO .

HE OSCILLOSCOPE PROJECTThis low cost test equipment project is a must for all electronics enthusiasts. It is a modular design,consisting of an X -Y Oscilloscope plotter and a separate 'Scope Module, containing the Y -Amplifier,

Time Base and Trigger circuits.The projected cost of the two modules is under £79-a price just too good to miss!

Designed essentially for audio work and for low -frequency digital test applications, future add-onmodules will include a transistor curve -tracer and a 10mV/cm preamplifier of cunning design for the

most sensitive audio operators.Part 1 of the HE Oscilloscope commences in the June '83 issue of Hobby Electronics.

A limited number of kits of components will be available through a leading electronics retailer, so be sureto order your copy in advance.

ZX COMPUTER SOUND BOARDAdd sound effects to your Spectrum or ZX81 games program with our ZX Sound Generator Board!

CB RAP LATCHKeep your eyes on the road keep your hands upon the wheel! Put Safety First with the HE Rap Latch.This simple device means you do not have to hold down the microphone PTT button while talking atlength. However, to ensure that the transmitter does not operate for ever, a simple timing circuit firstwarns that the latch is about to release, then switches the rig back to Receive after a preset time interval.

TRAFFIC LIGHT TOYA family project that has proved a smash hit (if you'll pardon the expression) with very young drivers.

THE ELECTRONIC REVOLUTIONOur popular informative series concludes with a review of the history of household electrical gadgets.

Please reserve

0 0

forName

0

J.

copies of the June issue of

Address

June issue on sale atyour newsagentfrom 13th May.

Place your order now!L J

Although these articles are being prepared for the next issue, circumstances may alter the final content.


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50 - 500v - uncos..1 - you select for VLTSALL ceded devices - NO duds Mm 50v50 for £1.00 - worth double ORDER NO Sx76

Silicon General Purpose NPN Transitors TO -18 Casey

Lock lit leads- coded CV7644 Similar to BC147- 8C107- 2189 ALL NEW, VCE ftly iC500mA

Ale 75-250 50 oft 100 on SOO on IWO on

PRICE £2.00 £3.80 £17.50 £30.00 gSilicon General Purpose PNP Transistors 10-S Case

Lock lit leads coded CV9507 similar 2N2S0SA to

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50 on 100 on 500 ot1 1000 on

PRICE £2.50 £4.00 £19.00 £35.00Order as CV9507

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100A Collection of Transistors. Diodes. Rectifiers. Bridges. SCR's

lilacs. IC's both Logic and Linear plus Opto's all of

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The Electronic Components and Semiconductor Bargain of the Year. A host of Electronic

componenrn including potentiometers - rotary and slider, presets- horizontal and vertical.Resisto nixed values 22ohms to 2M2 1/8 to 2 Watt. A comprehensive range of

capacitors ..,eluding electrolytic and pc'yester types plus disc ceramics etcetera.

Audio plugs and sockets of various types plus switches. fuses, healsinks, wire, nuts,bolts,

gromets, cable clips and lyes, knobs and P C Board Then add to that 100 Semiconductorsto include transistors. diodes, SCR's opto's. all of which are current everyday usable devices

in aH a Fantastic Parcel No rubbish all identifiable and valued in current catalogues at well

ver E25.00.Our Fight Against Inflation Price -- Beat the Budget

Down with Depression JUST E6.50.0/No. SX85

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Pak No. Qty' Description5116 250 Capacitors Mixed typesSX17 200 Ceramic Capacitors Miniature

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50-1000 mlS124 20 Tantalum Beads, mixed

L.:Quantities approximate, count by weight.

100100100

60

10050

LlLI

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IC SOCKETSThe lowest price ever.The more you buy the cheaper they COM&

Pon 10 off 50 off 100 off8 pin 86p E3.50 5.0014pin 90p E3.75 E8.5016 pin 96p E4.00 E7.0026 pin E2.50 E11.00 E20.00

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10220Positive + Negative +7805 - 50p 7905 - 55p1812 - 509 7912 - 55p7815 - 50p 7915 - 55p-824 - 50p 7924 - 55p

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20 Assorted Slider KnobsBlack/Chrome, etc. LI12 Neons and Filament Lamps. Lowvoltage and 'ruins - various typesand colours - borne panel mounting LI

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100 off £7.50Order No. AS: 4RIBRect.

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£1.50 each

'PROGRAMMABLE UNIJUNCTION TRANSISTOR"PUT" case T0106 plastic MEU22 Similar to2N6027/6028 PNPN SiliconPrice: 1-9 10-49 50-99 100, Normal RetailEach: 20p 18p 15p 13p Price £0.35 each

SX33A 6 small (min (SOST/SPDT ToggleSwitches 240v Samp £1.00

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SX71 50 BC108 "Fallouts" Manufac-turers out of spec on volts orgain You test. £1.00

S X72 A mixed bundle of Copper cladBoard Fibre glass and paper.Single and double sided. Afantastic bargain £1'13° A

SX38 100 Silicon NPN Transistors -allperfect Coded mixed types withdata and eqvt sheet. Inlo rejects.Real value. £3.80

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253055 The best known Power Transistors in theWorld - 2N3055 NPN 115wOur BI-PAK Special Offer Price10 oil 50 off 100 offL3.50 £16.00 L30.00

55312 COMPLIMENTARY PNP POWER .-.

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SPECIAL PRICE £0.70 each //10 off L6.50

I SINGLE SIDED FIBREGLASS IBOARD

Order No. Pieces Size Sq.Ins. PriceFBI 4 9 x 254" 100 £1.50FB2 3 11 a 3" 100 £1.50F83 4 13 x 3" 156 £2.00

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b- 703

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REGULATEDVARIABLEVARIABLEStabilisedPOWER SUPPLYVariable from 230 volts and 0.2 Amps. Kit includes -1 - VPS30 Module_ 1 - 25 volt 2 amp transformer.1 - 0.50v 2" Panel Meter, 1 - 02 amp 2" PanelMeter. 1 - 470 ohm wirewound potentiometer. 1 -4K7 ohm wirebound potentiometer. Wiring Downincluded Order No VPS30 KITMINIATURE FM TRANSMITTERFreq. 95-106MHz. Range: tv mileSize. 45 x 20mm Add: 9v bait. ONLYNot licenced in U.K £5.50Ideal tor: 007-M15-F8I-CIA-KGB etc. _di

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Project

StaAndy Armstrong

Our 'invisible',noiseless anti -theftdevice simulatesan ignition fault,frustrating a thief inhis attempt to makeoff with your motor.

THIS is a gadget which shoulddiscourage any thief in his right mindfrom stealing your car! Sure, you maysay, but a thief can get around anydisabling device in a few minutes.This one, however, doesn't appear tobe an anti -theft device; instead, itmakes the car seem to be at fault.

When the car engine is started(possibly not at the first try) it will runfor a few seconds, and then coughand die. Further attempts at startingwill be met with the same results.

This particular system has theadded advantage that it isautomatically reset when the ignitionis switched off, and that the methodof deactivating it is very unusual.Thus, you cannot forget to protectyour car, and any prospective thiefhas little chance of bypassing thesystem.

Obviously, the device can simply beremoved, so it needs to be installedwhere it won't easily be found -there are some suggestions about thisfurther on. The unit does its job byperiodically shorting the contactbreaker, and preventing a spark frombeing generated. Typically, it isshorted out for about two seconds inevery ten seconds; this is adequate tostop a cold engine, though one couldprobably continue driving if the carwas thoroughly warmed up andmoving reasonably fast.

This brings us to a WARNING:though the circuit is designed not tobring the car to a halt on a fast road,it is preferable to avoid even theslightest risk of this. Therefore, theanti -theft unit - and, indeed,anything which could stop the ignitionsystem from working - must be builtand fitted with reliability in mind (the

1 Thi

same applies to commercial deviceslike electronic ignitions).

The CircuitIC1a and b form a bistable whichalways powers up with pin 4 high andpin 3 low; this occurs because CItakes longer to charge than C2.Resistors R4 and R5, in series withpins 6 and 1 respectively, are toprevent the capacitor's dischargecurrents from damaging the CMOSinput protection diodes (built into thechip) when the unit is switched off, iewhen the ignition is switched off.

IC1c and d form an oscillator,which is enabled while pin 13 is heldhigh. This oscillation has an unevenmark to space ratio, so that the

NOTES:IC1 =40118

= BC108 etcD1,2 = 1N4148

TO TOUCHCONTACTS

R31MR

f

engine is allowed to function most ofthe time, but is periodically halted.The timing has been chosen so thatsomeone trying to restart the engineimmediately after it has stoppedwould meet with (temporary) success.

The oscillator works in the followingmanner: when the power is switchedon both C3 and C4 are uncharged;therefore at the moment of switch -on,pin 12 will be at logic 0. This causespin 11 to be at logic 1 and hence pin10 to be at logic 0. This state persistswhile the lower end of C4 chargestowards logic 1 via R9.

This same voltage will appear onpin 12 via R8, so that after it passesabout half the power supply voltage,pin 11 falls towards logic 0, causingpin 10 to rise to logic 1.

C2lOn

0-M/V.-R74k7

13

12

C3 R81n 10M

IC140118

11

R63308

D1

910680k

T fg;

8

IC1c

9

R91MR

10

C44u7

D

02

Figure 1. The Stall -Thief circuit;

0 4VEBATTERY

CONNECTION

CONTACTBREAKER

0 VEBATTERY

CONNECTION

Vcc connects to pin 14 of the IC and OV goes to pin 8.


Project MI

How It WorksThe Stall Thief is powered from apoint in the car's electrical systemwhich is switched on by the ignitionswitch. When power is applied, thebistable output is at logic 0 and 1 thisenables the oscillator, which is set upto produce an asymmetric waveform.The waveform is low' for most of theoscillator period, so that the relaydriver is turned off and the car maybe started - briefly!

However, when the oscillator

+12V (FROMIGNITION COIL/ 'I.

output is 'high' (for about twoseconds in every ten), the relay isenergised so that the contacts shortout the ignition coil contact breaker,effectively simulating a fault in theignition system.

The Stall Thief is disabled bytouching the concealed switchcontacts; this takes the bistableoutput to logic 0, disabling theoscillator and preventing the relayfrom operating.

TOUCH °SWITCH BISTABLE

ENABLEOSCILLATOR

Ul RE AY

RELAY

CONTACTBREAKER

In this condition, transistors Q1 andQ2, which form a Darlington pair, areturned on, thus closing the relay andpreventing the enging fromfunctioning.

You will observe, now, that thevoltage on the lower end of C4 isabout half the supply voltage higherthan the top end, which has just beenraised virtually to the full supplyvoltage. The voltage on C4 is thusoutside the limit of the supply railsand will therefore discharge, partly viaR8 and the input protection diodes onICld pin 12, but mostly via R9 andR10/D1. This is why R8 is such ahigh value - so that this dischargecurrent is small enough to be ignored,compared with the current through R9and R10.

The voltage on C4 thereforedischarges into ICld pin 11, towardslogic 0, with a time constant givenapproximately (neglecting R8) by C4,and R9 in parallel with R10 (since D1is conducting in this condition). Thistime constant is about 25% of thecharging time constant set by C4, R9because R9 in parallel with R10 isapproximately 520k.

When the voltage on pin 12 fallsbelow half the supply voltage, thelogic gates switch into the state theyhad when first switched on, thustaking the voltage on the lower end ofC4 outside the supply rails in theother direction, until it charges backup to half supply via R9 (see Figure 2).

This cycle repeats until the ownerof the vehicle touches both of the"touch plates"; this switches the flip-flop (ICla and IC1 b) into the otherstate, setting pin 4 at logic 0. Thisdisables the oscillator, causing pin 11to go to logic 1 and pin 10 to logic 0.Thus the relay is permanently de -energised and the engine runsnormally.

Spiking the NoiseThe purpose of C3 may not beimmediately obvious; it's there to

prevent stray noise pick-up onto thehigh impedance of pin 12, fromcausing spurious operation of thegate. The time constant of R8 and C3is much shorter than that of R9, R10and C4, so that C3 has no appreciableeffect on the oscillator frequency.

Since car electrical systems mayhave substantial voltage spikes onthem, the CMOS power supply isprotected by R6, D2 and C5; werethese components omitted from thedesign, the delicate CMOS wouldprobably fail at an inconvenientmoment!

Some constructors may wonder atthe use of a Darlington pair oftransistors to drive the relay - so aword of explanation. Even bufferedCMOS cannot properly be asked tosource much more than 1 mA (hencethe value of R11), and a transistor insaturation cannot be assumed to havea gain greater than ten. Therefore ifonly one transistor were used, acurrent of only 10mA would beavailable to drive the relay if thetransistor were saturated. What wouldhappen, in practice, would be thatsome unlucky constructors would findthat the relay did not pull in, or thatthe transistor burned out because itwas not properly switched on andthus was dissipating too much power.

ConstructionThe construction of the board issimply a matter of following theoverlay. The CMOS IC should beinstalled last, after a visual inspectionto check that the rest of thecomponents have been installedcorrectly.

Veropins can be used for theconnections to the board, though the0.25in push -on connector blades usedon the prototype are to be preferred.

The relay is separate from the boardfor two reasons: the first is that, whilea particular PCB mounting relay maynot be hard to obtain, many peoplemay have a 12V relay in theirjunkboxes. The second reason is that

DISTRIBUTORCONTACTBREAK ER

RLACONTACTS

BATTERY

HT TO

Dv(CHASSIS)

Figure 2. The circuit of a typical ignitionsystem; the Stall -Thief relay contactsshort out the distributor contact breakerintermittently, interrupting theignition timing.

PIN 12

PINS 89.11

PIN 10

JUNCTION OFC6.118.9,10

41-13 secs H

12V6

OV6

2'S,'

12V

- ov

-

OV

.e DIODE CHOPOUTSIDETHE RAILS

Figure 3. Waveforms produced at variouspoints in the Stall -Thief circuit when theoscillator consisting of IC1d,c is enabled(logic '1' on pin 13).

Parts ListRESISTORS(All 1/4 watt 5% carbon)R1,2,7 4k7R3,5,9 1MRR6 330RR8 10MR10 680kR11 10k

CAPACITORS(All polyester unless noted)Cl 100nC2 10nC3 ln

ceramicC4 4u7C5 10u

16VDC radial electro

SEMICONDUCTORSIC1 CD4011B

quad -NANDQ1,2 BC108

or similarD1,2 1N4148

or similarZD1 BCY88C12V

MISCELLANEOUSRLA see BuylinesPCB; case (see text); 6 x 1/4- PCB -mounting connector blades; wire,solder, nuts and bolts etc.

BUYLINES page 34


1111 Project

it may, under some circumstances, bepreferable to mount the relay near tothe distributor or coil, and mount therest of the works elsewhere, forexample behind the dashboard.

The choice of relay is, to someextent, important. The contacts needto be rated for the current (at least5A), and also need to open, when de -energised, to at least as wide as thecontact breaker gap, to avoid break-down. Some suitable types aredescribed in Buylines.

Once the unit is built it should betested before installation. Connect upthe relay and then connect the boardto a 1 2V power supply. The relayshould switch on for about twoseconds out of each ten. If it does notdo so, check the voltage across therelay coil; if this reaches at least 10Vfor the two seconds and still the relaydoes not switch, then it is unsuitable.

If there is no voltage on the relay atall, check the logic levels (afterswitch -on, before operating the touchcontacts!). A wrong or indeterminatelogic level should point to the shortcircuit, wrong component etc.

Once the relay has been made toswitch, slightly moisten your fingerand place it briefly across the twoblades waiting to be connected to thetouch terminals: the relay shouldswitch no more. Finally, it is a goodidea to varnish the board to avoidcondensation problems.

InstallationMany of the details of installation maybe left to the individual constructor, asthe space available in different carsneeds different methods.

The first decision to make iswhether to mount the relay separatelyor not. If there is little concealment forthe whole unit under the bonnet, it ispreferable to mount the relay near thewiring channels, and connect it to thecontact breaker in as unobtrusive away as possible. In this case, a small

:*:';:t.:;;::...;. 11.:4

4,4

.

pe

1.?

0. :40..

***"'

:: ". e:

TOUCH PLATES RELAY

R11

::::

RE LAYFigure 4. The component overlay; 1mm PCB connector pins may be used instead of thepush -on connectors, but are not as secure.plastic box just large enough to takethe PCB and push -on connectors isrequired. This may be mounted in aconvenient place behind thedashboard and wires run to the relay.If the area under the bonnet issufficiently untidy, so that an extraplastic box would not be noticed, thenthe whole thing can be mounted inone place, with twisted wires leadingto the touch contacts. For this option,a larger plastic box would be required.

In any event, the PCB should bemounted to the lid by four 6BA orM2.5 bolts, and a slot cut in the boxto allow cable entry. If the relay ismounted separately, it must besecurely bolted down; if it is mountedin the plastic box it may be easier touse double -sided adhesive pads ontwo faces to mount the relay. (Note:for a reliable fixing, the surfaces mustbe thoroughly clean.)

Since the wires from the relay tothe ignition system must be solderedat the relay end, special care shouldbe taken; these connections should besleeved, preferably with heatshrinksleeving (a 2kW electric fan heatershrinks it a treat!). These wires shouldalso be fixed in place using self-adhesive aluminium cable clamps,readily available from car accessoryshops.

The wiring to the contact breakershould be kept short to reduce theamount of extra ignition interferenceradiated, and on grounds of reliability.Depending on circumstances, a "piggyback" connector to the coil ordistributor, or a tap -in connector to

the wire between the two, should beused. Take care not to put tension onthe wiring, to avoid the risk of itpulling off while you are driving!

Touch contactsThe suggested techique for makingthese is to use plastic washers, of thetype used for transistor mounting, toput two bolts into the underside of thedashboard, but insulated from it. Ifthese bolts are more than a fewinches apart, it is most unlikely thatany one would touch both at once bychance, so your secret Stall Thiefwould be safe.

When the unit is fixed in place andconnected to its touch contacts, itshould be wired up to the battery.Assuming a negative earth, the -veterminal should be connected tochassis and the +ve terminal to anypositive supply which is switched offby the ignition switch (eg the +veterminal of the coil). For +ve earthcars, this procedure must, of course,be reversed.

OperationSimple! Switch on the ignition, thentouch both bolts without touching anyother metalwork (if your hands areexceptionally dry you may need to lickyour fingers but normally there shouldbe no problems). The car can then bestarted and driven as usual.

Your local tea -leaf, on the otherhand, will not know about this andwill be stalled in his attempt to stealyour motor. HE


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LOT 1. is a parcel of approximately 1 million 'A, X & 1 watt resistors.All uniformly packaged and front labelled in boxes ideal for retaildisplay.or self service racking. Normal stock valuation £6,000, offeredat E950 the lot.LOT 2. 1000 miniature encased relays - p.c.b. mounting - 2 change-over contacts 9 - 15V coil - very low current (700 ohm), normalstock valuation based one similar relay R.S. price £2.56 each isE2,500. Parcel offered for E600.

8 POWERFUL MODELMOTORS(all different)for robots, meccanos, drills,remote control planes, boats,etc. £2.95.

12 volt MOTOR BY SMITHSMade for use in cars, etc. these are serieswound and they become morePowerful as load increases. Size3`4" long by 3" dia. They have sesaa good length of 'A" spindle -Price £3.45.Ditto, but double ended £4.25.Ditto, but permanent magnet E3.75.

EXTRA POWERFUL 12v MOTORMade to work battery lawnmower, this probably develops up to

h.p., so it could be used to power a go-kart or to drive acompressor, etc. etc. £7.95 s- E1.50 post.(This is easily reversible with our reversing switch - Price E1.15).

SET OF 12v MOTORS!Set of four 12 volt motors to drive passenger locomotive - £29.50With address where to buy other parts.

WATERPROOF HEATING WIRE60 ohms per yard, this is a heating element wound on a fibre glasscoil and then covered with p.v.c. Dozens of uses - around waterpipes, under grow boxes in gloves and socks. 23p a metre.

THERMOSTAT ASSORTMENT10 different thermostats. 7 bi-metal types and 3 liquid types.There are the current stets which will open the switch to protectdevices against over load, short circuits, etc., or when fitted sayin front of the element of a blow heater, the heat would tripthe stat if the blower fuses: appliance stats, one for high temp-eratures, others adjustable over a range of temperatures whichcould include 0 - 100°C. There is also a thermostatic pod whichcan be immersed, an oven stet, a calibrated boiler stet, finally anice stat which, fitted to our waterproof heater element, up in theloft could protect your pipes from freezing. Separately, thesethermostats could cost around £15.00 -- however, you can havethe parcel for E2.50.

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Ditto - made upBig Ear, listen through walls

Robot controller - receiver/transmitter

Ignition kit - helps starting, saves petrol, improvesperformance

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Car Light 'left on' alarm

Secret switch - fools friends and enemies alike .

3 - 30v Variable Power Supply

2 Short & Medium Wave Crystal Radio

3v to 16v Mains Power Supply Kit

Light Chaser - three modes

(Willard Unilex Hi Fi stereo amplifier with speakers. .

Radio stethoscope . . .fauit finding aid

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for surveillance or normal FM

Soil heater for plants or seeds

Insulation Tester electronic meager

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Mixer Pre -amp (taco special with case

Aerial Rotator mains operated

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40 watt amp hi-li 20hz 20KHz

Microvolt multiplier measure very low currents withordinary multitester

E14.95

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E4.80

£250£2 99

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E6 90

£295E1600

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Pure Sine Wave Generator E5 75

Linear Power output meter £11 50

115 Watt Amplifier 5hz 25KHz ....... £13.50Power Supply for one or two 115 watt amps . . E17.50

Stereo Bass Booster, most items E8 95

1.5mm single1.5mm flat twin . .

1.5mm flat 3 core & E4mm single6mm flat 3 core16mm flat twin & E . . .

If not collecting, add 50% carriage.

INSTRUMENT BOX

Instrument box with key. Very strongly made (plywood sideswith hard board top and bottom). With black grained effect, vinylcovered, giving a very pleasing appearance. Internal dimensions12Vt" long, 4`4" wide, 6" deep. Ideal for carrying your multirange meter and small tools and for keeping them in a safe place.£2.30. Post paid if ordered with other goods, otherwise add £1.

LIGHTING & POWER CABLESCopper clad, PVC sheathed. Made by Volex to BSS.

per 100 metresper 100 metresper 100 metresper 100 metresPer 100 metresper 100 metres

SUB MINIATURE MOVING COIL SPEAKEROR MICROPHONE

£2.30£4.50E5.50

. £3.45£32.00E54.00

Beautifully made permanent magnet type, this is only 0.8" dia.and 0.4" thick lapproxl. Impedance approximately 350 ohms,voice coil sealed with dust cover. Ex -equipment.£1.15 each, or 10 for £10.

THIS MONTH'S SNIPSUPER BARGAIN JUST ARRIVED:The AMSTRAD Stereo Tuner.This ready assembled unit is the ideal tuner for a musiccentre or an amplifier, it can also be quickly made into apersonal stereo radio - easy to carry about and which willgive you superb reception.

Other uses are as a "get you to sleep radio", you could eventake it with you lo use in the lounge when the rest of thefamily want to view programmes in which you are notinterested. You can listen to some music instead.

Some of the features are: long wave band 115 - 270 KHz,medium wave band 525 - 1650KHz, FM band 87 -108MHz, mono, stereo switch, AFC switch, tuning meterto give you spot on stereo tuning, optional LED wave bandindicator, fully assembled and fully aligned. Full wiringup data showing you how to connect to amplifier or head-phones and details of suitable FM aerial (note ferrite rodaerial is included for medium and long wave bands. Allmade up on wry compact board. This comes packed in aspecial container, which you can use as a temporary case ifyou want to make it quickly into a carry about personalstereo.

Offered at a fraction of its cost: only £6.00s- £1.50 post insurance.

TANGENTIAL BLOW HEATER2.5 Kw quiet,efficient instantheating from230/240 voltmains. Kit consistsof blower asillustrated, 2.5 Kwelement, control switch and data all for £4.95. post £1.50.

MINI -MULTI TESTER Deluxe pocket size precision mov-ing coil instrument, Jewelled bearings- 2000 o.p.v. mirrored scale.11 instant range measures: DC volts 10, 50, 250, 1000.

AC volts 10, 50, 250, 1000.DC amps 0 -- 100 mA.

Continuity and resistance 0 - 1 meg ohmsin two ranges. Complete with test prodsand instruction book showing how tomeasure capacity and inductance as well.Unbelievable value at only £6.75 + 60p

post and insurance.

FREE Amps range kit to enableyou to read DC current from 010 amps, directly on the 0 - 10scale. It's free if you purchasequickly, but if you already own aMini -Tester and would like one,send E2.50.

J. BULL (Electrical) Ltd.(Dept. HE), 34 36 AMERICA LANE,

,HAYWARDS HEATH, SUSSEX RH16 3QU.Es blished30 YEARS

MAIL ORDER TERMS: Cash, P.O. or cheque with order. Orders underE10 add 60p service charge. Monthly account orders accepted fromschools and public companies. Access & 8icard orders accepted day ornight. Haywards Heath (0444) 454563. Bulk orders: write for quote.Delivery by return. Shop open 9.00 - 5.30, mon to Fri, not Saturday.

3 CHANNEL SOUND TO LIGHTNow supplied with fully prepared metal work and p.c.b.You'll have it going in an evening.

Complete kit of parts for a three channel sound to light unitcontrolling over 2000 watts of lighting. Use this at home if youwish but it is plenty rugged enough for disco work. The unit ishoused in an attractive two tone metal case and has controls foreach channel, and a master on/off. The audio input and outputare by 'A" sockets and three panel mounting fuse holders providethyristor protection. A four pin plug and socket facilitate ease ofconnecting ;amps. Special price is £14.95 in kit form or £25.00assembled and tested. Case & metal Chassis No. Fully punched andprepared.

PANEL METERS & INSTRUMENTSSingel meter, 200VAVolt meter 0 . 200 volts, Th" roundMilli errip meter. 50Orna T/s" round-amp meter, hot wire scaled, 0 - 9 ampsAmmeter, TO" round, centre zero, 500maCharger panel meters, 1 1:" dia. scaled 3 amp . . .

Panel meter, 1 5/8" square, scaled Vu . . . . .

Panel meter, Amstrad, 40rnm sq. centre zero, scaled 1, 2, 3.Edgeways panel, 3". 0 25ma, ex -GPO

SUPER HI -Fl SPEAKERCABINETSMade for an expensive Hi-Fi outfit- will suit any decor. Resonancefree. Cut-outs for 6S's" woofer andTO" tweeter. The front material isDacron. The completed unit is mostpleasing. Supplied in pairs, price£6.9d per pair (this is probably lessthan the original cost of onecabinet) carriage £3.00 the pair.

GOODMANS SPEAKERS6%." 8 ohm 25 watt E4.50. TO" 8 ohmtweeter. £2.50. No extra for postage ifordered with cabinets. Xover £1.50.

DITTO but for 8" speaker and 4"tweeter. £7.50 £3.50.

El 1 5El 75£1 15E2 30El 75

.75E1.15

.75£230

VENNER TIME SWITCHMaim operated with 20 amp switch, oneon and one off per 24 hrs. repeats dailyautomatically correcting for the lengthen-ing or shortening day. An expensive timeswitch but you can have it for only E2.95.These are without case but we can supplya plastic base £1.75 or metal case £2.95.Also available is adaptor kit to convertthis into a normal 24 hr. time switchbut with the added advantage of up to12 on/offs per 24 hrs. This makes an

ideal controller for the immersion heater.Price of adaptor kit is £2.30.

50 THINGS YOU CAN MAKEThings you can make include Multi range meter, Lowohms tester, A.C. amps meter, Alarm clock, Solderingiron minder, Two way telephone, Memory jogger, Liveline tester, Continuity checker, etc. etc., end you will stillhave hundreds of parts for future projects. Our 10Kgparcel contains not less than 1,000 items - panel meters,timers, thermal trips, relays, switches, motors, drills, taps,and dies, tools, thermostats, coils, condensers, resistors,neons, earphone/microphones, nicad charger, power Unit,multi -turn pots and data on the 50 projects.

YOURS FOR ONLY £11.50 plus £3.00 post.

EXTRACTOR FANSMains operated -- exeomputer.Woods extractor 4"x 4" Muffin 115v.

5" - E5.75, Post £1.25 E4.50. Post 75p.6" - E6.95, Post £1.25 4"x4" Muffin 230v.

5" Plannair extractor £5.75. Post 75p.£6.50. Post £1.25.

ROTARY WAFER SWITCHES5 amp silver plated contacts. '4" shaft. 1" dia. wafer.Single wafer types, 29p each. as follows:1 pole 12 way 2 pole 6 way4 pole 3 way 6 pole 2 wayTwo wafer type, 59p each, as follows2 pole 12 way 4 pole 5 way6 pole 2 way 8 pole 3 way3 wafer types 99p each,9 pole 4 way 6 pole 5 way

12p 3 way

EXTRA POWERFUL 12v MOTORMade to work battery lawnmower, this probably develops up toVS h.p., so it could be used to power a go-kart or to drive acompressor, etc. etc. £6.90 + £1.50 post.(This is easily reversible with our reversing switch Price £1.151.

MINI MONO AMP on p.c.b., size 4"x 2-approx. Fitted volume control and a holefor a tone control should you requireit. The amplifier has threetransistors and we estimatethe output to he 3W rms.More technical data will beincluded with the . -plifier.Brand new, peitt., cooffered at the vett, low p ice at£1.15 each. or 10 for E10.00.

3 pole 4 way4 pole 3 way

4 pole 6 way12 pole 2 way

6 pole 6 way18p 2 way


Famous Names

Charles ProteusSteinmetz

Ian Sinclair

An experimentor and teacher who took the guesswork out ofelectrical design.

YOU CAN BE FORGIVEN if you've neverheard of Charles Steinmetz, becauseneither his name nor his achievements arewell known on this side of the Big Pond.Nevertheless, his contribution to elec-tricity, and hence to electronics, has had aprofound influence on us all, makingpossible advances that we now take forgranted. Of all the Famous Names wehave looked at so far, that of Steinmetzseems at first glance least connected withmodern electronics, because most of hiswork was concerned with large electricmotors, but, as often happens, a piece ofresearch which expands usefulknowledge often affects work which iscarried out years later, and in an entirelydifferent field.

Steinmetz was born in Breslau, Ger-many, in 1865 (the town is now calledWroclaw, and has been part of Polandsince the occupation of Eastern Europe bythe USSR after the Second World War).He was christened Karl August Rudolf,and was handicapped from birth by asevere spinal deformity, which may havehad the effect of turning him to academicstudies at times when his classmateswere playing football. His education pro-gressed to the Technical High School inBerlin - a type of institution which neverbecame rooted in this country - and fromthere, in 1892, to University, where hestarted to make a name for himself as abrilliant researcher and equally as a com-mitted Social Democrat. It was this se-cond activity which drew him to the at-tentions of the ruling authorities, and it'sironic to think that if he were active in hishome town right now, the Polishauthorities would probably take the sameline.

After several brushes with the Govern-ment, he emigrated, like so many othersat the time, to the USA to find freedom ofexpression and action. Shortly afterarriving, he anglicised his names toCharles Proteus - Proteus having been acollege nickname.

His reputation as a researcher hadpreceded him, and he was employedalmost at once by the firm of Eickemeyerand Osterheld, an electrical manufactur-ing company with interests in electricmotors, transformers and powertransmission. Once established, hefounded a small research laboratorywhich soon became very well known in

the industry. It was at this laboratory thathe discovered the effect of magnetichysteresis.

Hysteresis LessonNow magnetic hysteresis isn't a subjectyou learn about nowadays unless youhave specialised interests. It was onceincluded as a topic in A Level physicscourses, but was dropped several yearsago because it didn't fit in with the newmethods of teaching physics, and in par-ticular with the modern system of units.This is a pity, because it deprives a lot ofstudents of their first glimpse of real -lifephysics, as distinct from the neat and tidy

cc

FORCE -I.-

Figure 1. The graph for stretchinga spring - providing you don'toverstretch it!

CC

0DECREASINGFORCE

'2[7,

INCREASINGFORCE

FORCE

Figure 2. The 'hysteresis' graph shapethat results from overstretching.

world of theory. Let me explain the sub-ject in outline.

When you stretch a spring, its lengthincreases, and the amount of force thatyou need to keep the spring stretcheddepends on how far you have stretched it.Unless you stretch the spring too far, itwill always return to its original lengthwhen you release it. This simple fact wasdiscovered by Hooke in the seventeenthcentury, and is called Hooke's Law. A lotof laws in physics are like this one - onequantity is proportional to another, sothat a graph of the extension of a springfor example, plotted against the stret-ching force, is a straight line (Figure 11.This type of relationship is called linear.

If you over -stretch the spring,however, its length is permanentlychanged, and the graph of extension plot-ted against force looks more complicated.The graph now has two lines, one for in-creasing force, the other for decreasingforce (Figure 2). A shape of this type iscalled a 'hysteresis' curve, and it implies,in this example, that the spring does notreturn to its original length.

Until Steinmetz investigated themagnetization of iron, everyone assumedthat when a coil of insulated wire waswrapped round a piece of iron, and anelectric current passed through the wire,then the magnetism of the iron woulddepend on the amount of current throughthe wire, and the relationship would belinear, or almost so. They expected, inother words, that a graph of magneticstrength plotted against current would bea straight line. By the late 1 880s, it wasbecoming obvious that this assumptionjust could not be sustained. There was,for example, no way in which the perfor-mance of an electric motor could bepredicted using these simple ideas aboutmagnetism, and the magnetism of theiron in the motor was the only missing linkin the theory. The only way that amanufacturer could get data on the likelyperformance of a new electric motordesign was to build a prototype and testit! At a time when the uses of electricity,and in particular the uses of electricmotors, were expanding rapidly, this wasunsatisfactory, rapidly becoming in-tolerable because the use of AC in powertransmission, strongly urged by manyengineers, demanded the use oftransformers - and there was no theory


Famous Names SEARCH COIL TO

DETECT MAGNETISM

BALLISTICGALVANOMETER

Figure 3. The Steinmetz apparatus, simplified. The rod was magnetized by thecurrent flowing in the large coil, and the amount of magnetism detected by thesmaller coil in conjunction with a ballistic galvanometer.

SATURATION LEVEL

CURRENT

Figure 4. The first part of themagnetizing curve for iron.

PERMANENTMAGNETISM

OR'REMANENCE'

DECREASINGCURRENT

INCREASINGCURRENT

CURRENT

Figure 5. The hysteresis effect - ascurrent is reduced from the saturationlevel, a different curve is traced, andwith zero current, the iron remainsmagnetized.

Figure 6. The complete hysteresis loop- the first part, marked OS, is seen onlywhen starting with completelydemagnetized material and is nevertraced again in the course of ameasurement of this kind.

governing the design of the most impor-tant part of a transformer, its magneticcore.

Round the BendSteinmetz set to work investigating themagnetism of iron and its alloys, using thetype of equipment illustrated in Figure 3.The details have been omitted, but theprinciple was that a measured currentwas passed through the coil surroundingthe magnetic specimen, and the strengthof the magnetism measured (by a systemwhich Steinmetz had devised). Themeasurements enabled him to draw agraph of magnetic strength (what wewould now call the flux density) againstthe current flowing in the coil (propor-tional to what we now call magnetizingforce). He started with completelydemagnetized iron, and found that as thecurrent increased, the magnetic strengthalso increased, following a curved graphline shaped rather like an 'S', to a maxi-mum magnetic strength, which hetermed 'magnetic saturation' (Figure 4).When the current was reduced, however,a different set of graph points was obtain-ed, so that the graph for decreasing cur-rent followed a different path. This path(Figure 51 showed that when the currentwas reduced to zero, the iron remainedmagnetized (the amount is caked the'remanence'). Steinmetz found that themagnetism could be reduced to zero onlyby reversing the direction of the current inthe coil and holding it at some definitevalue, called the 'coercive force'. Bytaking the value of the reversed current tothe amount that caused the magnetism tosaturate again he produced the now -familiar hysteresis curve for iron (Figure61.

The consequences of this work wereenormous. The area inside the loop -shaped curve is proportional to theamount of energy that has to be used tomagnetize and demagnetize the material,and this energy causes the iron to becomehot. Previously, it had been thought thatthe heating of electric motors andtransformers was due only to the currentflowing through the wires (and to eddycurrents, but Steinmetz's work clearlyshowed that the magnetic material wasas much to blame. He went on to showthat the shape and size (area) of thehysteresis curve could be greatly affectedby the composition of an iron alloy, and,even more importantly, on its previoustreatment, such as heating, previousmagnetization, mechanical strain, and soon.

For the first time, electric motors couldbe designed and perform to specification,and transformers could be wound whichwould not overheat. The way was openfor the invention of magnetic recording byPoulsen, and subsequent research whichled to the discovery of ferrite materialssuch as are now used for coil cores and foraerials in pocket radios. Even if Steinmetzhad done nothing more on this work, hewould have deserved to be remembered,and his classic paper of 1892 is wellworth reading in reprint form.

It Doesn't Add Up . . .

He contributed much more, however.When he arrived in the USA, he wasamazed and dismayed to find thatengineers, brought up in the British tradi-tion, were almost incapable of makingelementary calculations on alternatingcurrent circuits, and he undertook, vir-tually singlehanded, to raise the level ofmathematical education to the standardwhich by then was common on the Euro-pean continent, Britain excepted. He in-vented a new method of expressing ACcalculations (the j -vector method) whichis still in use, and, finding that engineersdidn't understand it or even appreciate itsadvantages, he set about writing, in1897, a textbook of EngineeringMathematics which did more to improvethe education of engineers than any othersingle step in the decade.

Steinmetz's reputation by that timewas such that when General Electric pur-chased the firm of Eickemeyer andOsterheld, Steinmetz was regarded as themain asset, and the most valuable singlepart of the deal. His work for GE included anew theory of transients (voltage pulses)which resulted in greatly improved waysof protecting transmission lines againstswitching surges and lightning strikes.The same theory was later used by theearly workers on radar to predict the ac-tion of pulses in their circuits. Always anexperimenter as well as a brilliant theorist,Steinmetz designed a pulse generator, fortesting lines, which would evennowadays be regarded as somethingspecial - 100kV at 10kA for 1 ns! Thisgiant insulation -cracker was used to testlines for transient behaviour - and onenanosecond is as transient as you canget.

He continued working for GE, living intheir bachelor accommodation surround-ed by dozens of pet small animals of everykind, and a hothouse full of his special joy,orchids. He appears to have been idolisedby his fellow -workers as that very raretype, a near -genius who was at the sametime a very warm and friendly personality,and who would help anyone to the best ofhis ability. He died in 1923, havingamassed no fortune, won few of the glit-tering prizes that most academics covet,and not even honoured by having hisname used for a unit or a device. The ad-miration of his colleagues, and the in-creasing value of his contributions to elec-trical science were reward enough forCharles Steinmetz, and perhaps this arti-cle may serve to make his well -deservedUS reputation rather better known overhere. HE


HE PROJECT KITS I C TOOLS CASES

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Reprints available separately 46p each + p. ft p. 40p.STEREO VOICE OVER UNIT April83 Med linking wire extra 14p metre£17.52 COMBINATION LOCK Oct 81 lessOPTIONAL MIC PRE AMP April 83 (no solenoid £18.66case) £4.28 BABY ALARM Oct 81 £8.70. Fig 8 linkingAUTO POWER DOWN April83 no case wire 7p metre£8.05 'DIANA' METAL LOCATOR Sept 81PHASE FOUR Dec 82 £18.71 54.50STEREO NOISE GATE Dec 82 r15.35 REACTION TESTER GAME Sept 81TAPE/SLIDE SYNCHRONIZER Dec 82 £12.81f21.73 VARIABLE BENCH POWER SUPPLYBIG EAR Dec 82 less pipe parts E1.21 Aug 81 E26.98MICROAMMETER ADAPTOR Dec 82 ULTRASOUND BURGLAR ALARM5.98 July 81 £19.98

ODOMETER Nov. 82 £14.98 ELECTRONIC DOOR BUZZER July 81DIANA V.C.O. Nov 82 1E4.89 5.98CO SQUELCH UNIT Oct 82 E9.19 ELECTRONIC METRONOME July 81'JUNIOR' SLOT CAR CONTROLLER £4.99Sept 82 f5.60 less case. CONTINUITY CHECKER June 81 5.712X INTERFACE BOARD Sept 82 inc ENVELOPE GENERATOR June 81edge con £11.33. 57.98T.V.I. FILTER July 82 £5.33 AUDIO MIXER June 81135.33AUTO WAH June 82 £18.98 inc case or PUBLIC ADDRESS AMPLIFIER March£1228 less case. 81 £19.48. Extras - horn speakers £5.83AUTO GREENHOUSE SPRINKLER each, PA MIC £4.40June 82 E15.38 less pump and power FUZZBOX March 81 [10.98Ripply I12V 2A). WINDSCREEN WIPER CONTROLLERTELEPHONE TIMER June 82 f33.42 less March 81 £8.20power supply (suitable type below). STEAM LOCO WHISTLE March 81POWER SUPPLY DESIGN 12V 500mA 52.98June 82 f9.98 PHOTOGRAPHIC TIMER March 81ECHO REVERB UNIT May 82. Less case £3.50E33.98. Economy case WB3 £3.76 extra HEARTBEAT MONITOR Feb 81 £24.98DIGITAL THERMOMETER May 82 ex- TWO-TONE TRAIN HORN Feb 81 £5.60eluding case + bezel £16.90 less caseAUDIO SIGNAL GENERATOR May 82 medium wave radI6 Feb 81 £820120.98. BENCH AMP Jan 81 £10.80CABLE TRACKER May 82 E9.96 NICAD CHARGER Jan 81 £820DIGITAL CAPACITANCE METER Apr CHUFFER Jan 81, less case f7.5382 £21.37 BATTERY CHARGE MONITOR Dec 82SIGNAL TRACER Apr 82 £3.86 5.77BIKE ALARM Apr 02 £11.74 MEMORY BANK - MINI SYNTH -DIGITAL DICE Mar 82 £729 MISER Nov Er Dedc 90 £39.98BICYCLE SIREN Mar e2 £10.89 TRANSISTOR TESTER Nov 81 E15.54 incNOISELESS FUZZBOX Feb 82 £10.45 test leadsMASTHEAD AMPLIFIER Feb 8:2 £14.74 GUITAR PRE -AMP Nov 80 £6.65DRUM SYNTHESIZER Dec 81. Full kit case ldiecast) extra f2.29121.37 INTRUDER ALARM Oct 80 E20.98GUITAR HEADPHONE AMPLIFIER TOUCH SWITCH Sept 80 f2.75 less caseDec 81 £3.72 & contactsIN CAR CASSETTE POWER SUPPLY GUITAR PHASER Sept 80 £16.28Dec 81 £4.77 SOUND OPERATED FLASH TRIGGERSCRATCH FILTER Nov 81 Mono E5.82 July 80 no slit £5.33Stereo £8.98 FOG HORN June 80 5.64LED VU METER Nov 81 less case £4.87 SPEED CONTROLLtH t-uet HP: Apra nuSIMPLE STYLUS ORGAN Nov 81 less £17.56 (less case)case E4.98 UlLiITAL FREQUENCY METER April 80METRONOME Nov 81 £12.71 £39.98TELEPHONE BELL REPEATER Oct 81 GUITAR TUNER Nov 79E12.6253.87 CAR ALARM Feb 79 £12.91

MORE PROJECT KITS - SIMILAR STYLE TO H.E.INSTRUCTIONS INCLUDED (SEPARATELY 45p EACH)PLEASE QUOTE REF. NO. WHEN ORDERING

61 PEST CONTROL 'Ultrasonic catsoarer' £7.6582 COMPONENT TESTER £8.8884 GUITAR NOTE EXPANDER £17.98136 CAMERA OR FLASH GUNTRIGGER Infra red system C12.6186 SIMPLE INFRA RED REMOTECONTROL E17.20B70 -12V POWER SUPPLY E17.98B9 SOUND TO LIGHT - single channel13.42810 THREE CHANNEL SOUND TOLIGHT £21.44

B11 IN SITU TRANSISTOR TESTER5.98612 WEIRD SOUND EFFECTSGENERATOR £5.98B13 AUDIBLE VISUAL METRONOME55.98

B14 ELECTRONIC DICE £5.71

B16 MINI EGG TIMER £4.34818 LED JEWELLERY - Cross brooch12.77 Star brooch E9.91 Spiral broochf7.98

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1982 ELECTRONICSCATALOGUE

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SOLDERINGANTEX X5 SOLDERING IRON

SOLDERING IRON STANDSPARE BITS. Small standard,66p each. For X5 + X2.5SOLDER. Handy sizeSOLDER CARTONDESOLDER BRAIDHEAT SINK TWEEZERSDESOLDER PUMPHOW TO SOLDER LEAFLETLOW COST CUTTERSLOW COST LONG NOSE

WIRE STRIPPERS Et CUTTERS..PRECISION PETITE12V P.C.B. DRILLDRILL STANDGRINDING STONEGRINDING WHEELSAW BLADEBRASS WIRE BRUSHBURR

VERO SPOT FACE CUTTERPIN INSERTION TOOLVEROPINS Ipk of 10010.1"MULTIMETER TYPE 111.000

MULTIMETER TYPE 2120,000with transistor tester. Very good

CROCODILE CLIP TEST LEAD10 leads with 20 clips

MULTIMETER TYPEYN360 TR, £14.75

25W£6.48

. £1.98large,

£1.84

Eta

£1.89PLIERS

£1.68£2.69

51.67£7.98

£1.495.98

52poov)

£5.48opvl

£14.75SET.99p

2 -

I TOOLSRESISTOR COLOURCALCULATORCONNECTING WIREED. 11 coloursILLUMINATED MAGNIFIERS

Small 2" dia. (5 x99P Large 3" dia. (4 x

CAST IRON VICE69p SCREWDRIVER SET29p POCKET TOOL SET

DENTISTS INSPECTION

12p JEWELLERS EYEGLASSPLASTIC TWEEZERSPAIR OF PROBESIccl .

. .

60p50p85p60p - '50p .......

....,

20,000 opv. Includes transistorAC + DC volts. DC current.

useful resistanceWe've used it and

CODE21p

PACK TYPE49p

mag.l ... E1.14magl £2.40

E2.98£1.98£3.98

MIRRORf2.86£1.60

69pWITH LEADS

77p

+ww...

...

tester.4 very

ranges.we like it.

SPEAKERS. Miniature, 8 ohm II7p MIN. BUZZERS. 6V. 500. 9V. £1 10.64-75 ohm 011p I2V. 65,.CRYSTAL EARPIECE 65p MAGENTIC EARPIECE 15pMONO HEADPHONES E2 96 STEREO HEADPHONES ES 35TELEPHONE PICK-UP COIL . 72p F.M. AERIAL 49p

VEROBOARD 0.1" COPPER STRIPS t10 strips 24 holes E1.20 per 524 strips 37 holes 79p24 strips 50 holes top36 strips 37 holes 59936 strips 50 hots. 999Terminal pins 0.1"520/100

PP3 CLIPS 10pPP9 CLIPS 1Ip PANEL METERS

WuA 1000A; I rnA,1A, 25V. 100uA-0-100uA; 5A AU54.98 each. Statevalue

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JUNIOR HACKSAW ...... ._ ..... __My magnifier attached. used and recom-SPARE BLADES 290/3 I mended On out staff.ABRAFRAME HACKSAWlaw all directions) .570SPARE BLADES .360/2QUICKTEST (Quick connect mains block)..E6.99

30 SOLDERLESS BREADBOARDBook by R.

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(Less batteries) £24 74

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ADVENTURES WITH ELECTRONICS

ADVENTURES WITHMICROELECTRONICS

Similar to 'Electronics' below.Uses I.C.s. Includes dice, elec-tronic organ, dcorbell, reactiontimer, radio, etc. Based on Bim-board 1 bread board.Adventures with

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by TO111

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An easy to follow book suitable for all ages. Ideal for beginners.No soldering, uses an S -Dec breadboard. Gives clear instructionswith lots of pictures. 16 projects -including three radios, siren,metronome, organ, intercom, timer, etc. Helps you learn aboutelectronic components and how circuits work. Component packincludes an S -Dec breadboard and all the components for theprojects.Adventures with Electronics £2.40. Component pack £18.98less battery.


Project

AerWithout WingsAndy Armstrong

A novel device that converts a rear-

window demister into an effective carradio aerial for medium or longwavereception.ARE YOU fed up with car aerials thatcorrode and won't work properly, orwhich are broken off by vandals? Orperhaps you simply dislike the idea ofdrilling rust -trapping holes in yourbeautiful bodywork!

If you listen to long or mediumwave radio in your car, then yourtroubles may be over. This simplegadget will transform a rear windowdemister into a long and mediumwave aerial; it will also work for FMreception, though not so well becauseof directional effects.

Circuit, What Circuit?All you need to build the device is acouple of capacitors and a bifilarwound coil. The circuit, such as it is,is shown in Figure 1.

The demister, like any length ofwire, straight or not, will act as anaerial, but normally the radiofrequency voltages induced in thewire are shorted to earth, eitherdirectly or through the battery (whichpresents virtually zero impedance tohigh frequencies).

The effective part of the circuit isthe bifilar-wound coil, L1, whichpresents a high impedance to radiofrequency signals, allowing them tobe tapped off to the car radio aerialinput via Cl. The 1 n capacitor, C2,is there to bypass to earth anytransients (spikes) which are oftenpresent on a car's electrical system.

But what, you ask, is a "bifilar

coil"? Well, it is simply two coils (likea 'pair' of scissors, there must be two'halves') wound on a common formerfor the same number of turns with thesame gauge wire, and in the samedirection. The dots at the ends of thecoil, in the circuit, indicate either thestart or the finish of each winding; itdoesn't matter which, as long as bothends are the same (this is the so-called 'dot convention' which is thestandard way of indicating the polarityof transformers etc.).

Saturation TacticsWhenever a current flows in a coil (orin any wire, for that matter), amagnetic field is set up around theconductor. If the current is DC,however, and if the coil is wound onan iron or ferrite core, the magneticflux rapidly reaches 'saturation',beyond which further increases incurrent have very little effect.

Therefore the high frequency ACwill have no effect, either, and sinceinductance is largely dependent onvariations in the magnetic fluxdensity, DC flowing through an iron orferrite -cored inductor has a drasticand undesirable effect on theinductance.

Bifilar-wound coils prevent this;since the coils, when connected asshown in Figure 1, are passing thesame DC in opposite directions, themagnetic fields in each half are ofopposite polarity and therefore cancel

TO AERIAL

FROMDEMISTER

SWITCH .1-- DEMISTER

Figure 1. The Circuit: dots signify the starting points of the two windings.

out. Thus only the flux due to the AChas any real presence, and the valueof the inductance can be accuratelypredicted.

Construction andInstallationTo make the coil, you simply need towind two strands of thick wire(preferably 1.2mm2 enamelledcopper wire, but ordinary 1 3Ahousehold cable will do) on a toroid orpot former for between 13-20 turns,taking care to wind them together andin the same direction. Obviously thenumber of turns is not too criticalwithin this range, so there is someroom for experiment here! C2 can besoldered across the ends of the coilbut the other capacitor cannot be soconveniently mounted, so aftersoldering to the appropriate coil -end,it must be securely fixed to part of thecar body using a plastic cable tie.Alternatively, it could be strappedacross the body of the toroid or potformer with a longer plastic cable clip,which can also be used to secure thewhole assembly to the car chassis.

As with all constructions to be usedin a motor, the soldered connectionsmust be very secure lest they vibratethemselves loose, and all bare wiresshould be covered with insulatingsleeving, preferably of the heat -shrinking variety.

The completed device should beinstalled as close as possible to thedemister, to avoid interference pickup,and is connected to the radio aerialinput via a long length of lowcapacitance car aerial cable, availablefrom most good motor accessoryshops. Do not be tempted to useordinary co -ax, as the high inherentcapacitance of this type of cable willprevent correct operation.

Next the car radio aerial trimmermust be adjusted for best reception;this can usually be done withoutdismantling the radio, and the locationof the trimmer will be explained in thecar radio installation instructions.And, finally, it may be necessary toimprove the interference suppression,either by replacing the existingsuppression components or addingextra ones (again, these should beavailable from an accessory shop).So here's wishing you happymotoring, and easy listening pleasure.Your car aerial is now off the wing!

Parts List HE

CAPACITORS(polyester)C1 10nC2 1n

MISCELLANEOUSsee text

Pot core or toroid (see Buylines);1.2mm2 wire; car aerial cable;motor car with rear window de-mister and car radio.

BUYLINES page 34


Project

This handy little testgadget will help yousort out all thoselittle things that gowrong in auto-motive electrics.With this, you cancheck voltagedrops, on and offcharge batteryvoltages andresistances.

H E Auto TesterGraeme Teesdale

BUDDING MECHANICS are very oftenbamboozled by the electrics of amodern motor vehicle. An automotiveor electronic type multimeter, with itscombination scales all crammedtogether, simply adds to theconfusion. This project was developedto make fault-finding a little easier byproviding simple LED indication of'set' points in voltage or resistance.

In a vehicle, voltage drop in cablesof more than OV5 can bringproblems. The Auto Tester provides aclear indication of voltage drops lessor greater than OV5. The batterysystem, to perform up to scratch,must deliver at least 12V on load andthe battery should have a terminalvoltage of more than 13V5 whencharging.

Resistances encountered in vehiclestend to have fairly well defined limits.Many devices have resistances under10 ohms, a few range up to 150ohms. Thus the first resistance 'set'point is at about 150 ohms. Muchhigher resistances are encountered inHT suppressors, etc. Generally, theseare around 10k or 15k. Trouble canoccur if they go faulty and exhibit ahigh resistance, generally greaterthan 50k. Thus, two other 'set' pointsfor resistance are at 10k and 50k.

The unit was housed in a small,conveniently -sized box; the PCBdesigned for the unit will just fitcomfortably into several differenttypes on the market. Four indicatorLEDs are provided: a POLARITYindicator, followed by one for each ofthe three set points in voltage andresistance. Two pushbuttons selectwhich 'mode' you wish to use -VOLTS or OHMS.

Where battery polarity is unknown,or in instances where the Auto Testermay be incorrectly connected, thePOLARITY LED will light when thered, or positive, input lead isconnected to the battery negative.

Protection against input overvoltagedamage has been incorporated, sothat voltage inputs of greater than

HE Auto Tester showing the frontpanel and crocodile clips.

15V are clamped to avoid damagingthe IC.

The Auto Tester, unlike most multi -meters, will not be damaged if a DCvoltage is applied to the input when itis being used in the resistance mode.

The unit is powered from a PP3 9Vbattery and the circuit is based aroundthe commonly available, low costLM324 or uA324 quad op -amp. Thebattery will likely last its shelf life(probably a year or more) asconsumption is only ever momentary,when you take a reading!

Auto TestingThe clearest way of seeing how thiscircuit works is to break it down intosimplified sections. The Auto Testerperforms three main functions:voltage drop measurement, 12/13.8Vmeasurement and resistancemeasurement. In addition, anindication of reverse polarityconnection is provided along withinput overvoltage protection.

The whole circuit is built around anLM324 (or uA324) quad op -amp, IC1.Three op -amps from this are arrangedas comparators and one as anamplifier. Let's look at the voltagedrop measurement stage first. Thisportion of the circuit is shown inFigure 1 (only the relevantcomponents are included).

When PB1 is pressed, power issupplied to IC1 via D3 (note that R1,LED1, R2 and ZD2 play no part here).RV1, R3 and R4 form a voltage divideracross the input of IC1 a, which isarranged as an amplifier, while ICidis set up as a comparator.

If the input leads are then


Project

INPUT

R147R

R2180R

RV1100k

R382k

ZD2 r

0

R4100k

R5 D14k7 R9

LED1

R710k

12k

R8820R

R108209

Figure 1. The Auto Tester circuit.

INPUT

R113k3

Figure 2. Voltage drop measurement.

INPUT

6

9

10

13

D3

ZD17V5

R131509 F,

R141509

915

14 150R

LED2

LED 3

11 LED4

NOTES:ICI = LM324D1-3 = 1N4148LED1-4 = 0.2" REDZD1 = 7V5ZD2 = 15V

R113k3 IC1

PIN 4

Figure 3. 12V and 13V8 measurement.

connected across a cable having avoltage drop of less than half a volt,say OV2, the voltage appearing at thenon -inverting input of IC1a will beabout OV1 (half the input volts) due tothe divider action of RV1, R3 and R4.RV1 is set to provide this division ratioof about two, while IC1 a provides again of 10, and thus the output will be1V. This is lower than the 2V6 on thenon -inverting input of !Cid and thusits output will be driven high, lightingLED4.

D3

R16

1009

PB1VOLTS'

0 PB2'OHMS'

-r B19V

PB1'VOLTS'

0 +9V

-7-0 +9VPB1

VOLTS'

If the voltage drop on the cable youhave connected the input leads acrossreaches a little over a half a volt, sayOV55, the voltage on the non -inverting input of IC1a will be OV275.The voltage on the output of IC1a, andthus the inverting input of IC1d, willbe 2V75 which exceeds the 2V6 onIC1d's non -inverting input. The outputof !Cid will thus go low and LED4 willextinguish, warning you of excessivevoltage drop in the cable.

Note that, when performing voltage

drop measurements, the positive leadmust be connected at the end of thecable closest to the positive terminalof the vehicle battery!

When the input leads are opencircuit and PB1 is pressed, D1 will beforward biased as it is connected tothe 7V5 rail (from ZD1) via R8. Thus,something a little under 7V willappear at the 'top' of RV1, and about3V5 at pins 3, 5 and 10 of IC1. Thiswill drive the output of IC1 d low, andLED4 will be unlit. It won't change thecondition of either IC1c or IC1 d, soLEDs 2 and 3 will also be unlit. Thus,nothing happens if you press PB1('VOLTS') when the leads are notconnected to anything.

Let us look at the other voltagemeasurements now. This section ofthe circuitry is shown in Figure 2,where IC1b and IC1 c are connectedas comparators. Each has its invertinginput connected to the voltage dividerR9, 10, 11 and 12. This voltagedivider is supplied from a regulated7V5, derived by ZD1 and R16,thus battery voltage variations will notaffect circuit operation, provided thebattery voltage doesn't fall to 8V orless.

IC1b and IC1c have their non -inverting inputs connected togetherand these are attached to the inputvoltage divider. When PB1 is pressed,power is supplied to IC1 via D3, asbefore. With no input voltage, theoutputs of IC1 b and c will both be lowand LEDs 2 and 3 will be unlit. Whenthe input leads are connected to avoltage a little over 12V, the voltageon pin 10 of IC1c will be a little over6V. This will drive the output of IC1 chigh, lighting LED3. When the inputvoltage rises above about 13V5, thevoltage on the pin 5 of IC1b will be alittle over 6V7, driving the output ofIC1b high, now lighting LED2 also.

ResistanceLook at resistance measurement now(for this explanation, refer to thecomplete circuit diagram, Figure 3).As before, R1, LED1, R2 and -ZD2 playno part here.

When PB2 is pressed, power issupplied to IC1 via D2; some currentis also supplied to the resistive dividernetwork, R9, 10, 11, 12, by R8. Thisestablishes a different set of voltageson the three comparator inputs. Pin 6,IC1 b will now have about 3V8 on it,pin 9, IC1c about 3V on it and pin 12,IC1d about 1V3 on it.

When the leads are connected to aresistance, current will be supplied tothe resistance via D1 and R5. Say theresistance is 100 ohms; about 1 mA8will be driven through it becausethere is about 8V5 on the cathode ofD1 and 8.5 divided by 4800 ohmsgives about 1 mA8. Thus, there willbe a voltage drop across the 100ohms of resistance of about OV18.About OV09 will appear on pin 3,IC1a, and the output of IC1a will drivethe inverting input of ICid to aboutOV9 which is less than the 1V2 onIC1d's non -inverting input. Thus the


? ro j ect

output of ICld will be high, lightingLED4. If the resistance across theinput is, say, 180 ohms, the voltageacross the input leads will be aboutOV32. About OV16 appears on pin 3,IC1 a and IV6 on pin 13, ICI d. Theoutput of IC1d will therefore go low,and LED4 will not light.

If the resistance across the inputterminals is between 150 ohms and10k, say 5000 ohms or so, then thevoltage across it will be about 4V. Thevoltage on pin 10, IC1c will be about2V, which is less than that on pin 9and the output of IC1c will be low andLED3 will be unlit. If the resistanceacross the input leads is about 15k,say (such as a spark plug suppressorresistor), then the voltage across theinput will be about 6V4 and thevoltage presented to pin 10, IC1c willbe about 3V2. This is above the 3V onpin 9 and the output will thus go high,turning on LED3.

If the resistance across the inputleads is about 50k, then the voltageacross the input will be about 7V8.The voltage on pin 5, ICI b will beabout 3V9 and the output of IC1b willtherefore be high, turning LED2 on.Note that LED3 will also be on as thevoltage on pin 10, IC1c is above thaton pin 9 and ICI's output will be highalso. Thus, for all resistances above50k (including an open circuit) LED2and LED3 will light.

Parts ListRESISTORS(All 1/4 watt 5% carbon)R1R2R3R4

47R180R

82k100k

R5,12 4k7R6 1kR7 10kR8 12kR9,10 8208R11 3k3R13,14,15 150RR16 100R

POTENTIOMETERSRV1 100k

min trimpot

SEMICONDUCTORSIC1 LM324

quad -op ampLED1,2,3,4 0.2" red LEDsD1, 2, 3 .1N4148 etc.ZD1 7V5 ZenerZD2 I5V Zener

MISCELLANEOUSPB1,2 push -to -make

switchesPCB; box approx. 52 x 30 x 100mm;PP3 battery plus clip; 2 x alligatorclips and leads; wire, solder, nutsand bolts etc.

BUYLINES page 34

Poles ApartFollowed that so far? Alright, let's lookat the reverse polarity indication. Therelevant portion of the circuit isshown in Figure 4.

If the input leads are transposedwhile trying to measure voltage, ZD2will conduct as a diode in the forwarddirection (as shown by the arrow),passing current through LED1, whichwill turn on. It will also pass somecurrent through R1, but that'simmaterial. R1 is there so that currentcan pass to RV1 when the leads arecorrectly connected, otherwise nocurrent would pass through LED1 asit would appear as a reverse -biaseddiode.

If you reverse the input leads whileattempting to measure voltage drop,LED1 will only come on if the voltagedrop is above about 1V3 or so. Thus,it is important to watch lead polaritywhen measuring voltage drop incables.

Overvoltage protection is providedby ZD2. Why have it? Well, if a batterycable comes adrift and you'reattempting to measure voltages whilethe motor is running, the generator/alternator can quite easily deliveroutputs of 20V or so; this can possiblydestroy the LM324. In addition, it isnot unusual to get inductively -produced voltage 'spikes' on thesupply lines in a vehicle, which canalso destroy the IC. If a voltage ofgreater than 15V appears on the inputleads to the Auto Tester, ZD2 willensure that the voltage delivered tothe LM324 does not exceed 15V.

The various voltages andresistances given here can vary by ±10% or so without grossly affecting

LE DI0111

R 2 1--

ZD2

104--I R3 1--

--I R4 I --

R147R

R2180R

ZD215V

GREATERTHAN 15V

-eLED1

TO RV1 ANDREST OF CIRCUIT

Figure 4 (top). Reverse polarityindication.Figure 5 (bottom). Overvoltageprotection.

your interpretation of readings. Whatyou are after, after all, is a 'ballpark'measurement which will indicate if allis well, or not.

ConstructionThe project PCB has been designed tofit into almost any of the smallgeneral purpose boxes available.These are generally all -plastic orplastic cases with a light gaugealuminium 'lid'. The design will suitthose boxes measuring 52 x 100mmor a little larger.

Before assembling the componentsto the board, check that it has no

LED2 LED3

71- 0 -LI- 0 4-

T TT T

cc

--I R11 I ---

" T T

Figure 6.Component overlay.

D

'D 0

'OHMS'

D3

D2

--1 R8

1 1

L ED4

0

0I 'VOLTS'


Project

NOT USED

LIGHTS WHENRESISTANCE IS

BELOW 150 OHMS

'RESISTANCE' MODE

0 0

AUTO TESTER

(0-150- -10k- 50k)

©12 13.8)

OHMS VOLTS

0

PRESS THIS BUTTON

LIGHTS WHENINPUT POLARITY

REVERSED

LIGHTS WHENRESISTANCE10k OR ABOVE

LIGHTS WHENVOLTAGE DROPLESS THAN 0V5

GOES OUT WHENVOLTAGE DROP

EXCEEDS OV5

LIGHTS WHENRESISTANCEABOVE 50k

VOLTS' MODE

0 0

AUTO TESTER

10-150 10k 50k)

OvoLnnrt

0(0.5 12 13.8)

OHMS VOLTS

o To

LIGHTS WHENVOLTAGEABOVE 12V

LIGHTS WHENVOLTAGEABOVE 13V5

PRESS THIS BUTTON

Figure 7. Operating the Auto Tester in Resistance and Voltage modes.

12V BATTERY

I -

20kPOTENTIOMETER

MULTIMETER

Figure 8. Test setup for calibrating the Auto Tester.

breaks or shorts between tracks,particularly between the IC pins. Alsocheck that components like RV1, theZener diodes and LEDs have thecorrect lead hole sizes drilled. Theboard can be mounted by solderingthe two pushbutton switches directlyto the board and letting the boardhang from their leads - it's quite arobust arrangement. If you're going todo this, see that the holes for PB1 andPB2 are drilled the right size.

Next, check that the board fitsinside the box. Make sure you orientthe board correctly when you do this.If the board doesn't fit in withoutjamming you may have to carefullytrim a little off one or both sides witha file until it fits properly. If it doesn'tfit at all, get a bigger box.

Mark out and drill the front panel,or lid, of the box and fit the four LEDmounts. Once the board is ready togo, commence assembly by solderingall the resistors in place, then thediodes D1, 2 and 3, followed by the

AUTOTESTER

0 0 0 0

two Zener diodes (make sure you getall the diodes in the correct wayround).

If you're mounting the board to PB1and PB2, solder these in place now,making sure their mounting'shoulders' are level. Insert the fourLEDs next, but don't solder them inplace; make sure you orient themcorrectly and don't trim off their leads.Temporarily mount the board to thefront panel of the case, push the LEDsinto position and then solder and trimtheir leads. De -mount the board fromthe panel and fit IC1, RV1, the batteryclip lead and the two input leads. Nowyou're ready for testing. But first,check everything carefully. See thatthe IC, all diodes and LEDs arecorrectly orientated, according to thecomponent overlay.

Testing the UnitFit a 9V, PP3 battery, short the inputclips together and press the VOLTS

BEFISTIES

button: the OV5 LED should come on.If not, check component orientations,then resistor values. Fix any faults,and once you have that corrected, tryagain. When you get the OV5 LED tolight, unclip the input leads and itshould go out.

To calibrate the unit, you'll need toget hold of a multimeter, a wellcharged 12V battery and a 20kpotentiometer. Hookup the circuitshown here and adjust thepotentiometer to give a 12V readingon the multimeter. Press the VOLTSbutton and adjust RV1 so that the'12V" LED just lights. Then, reset thepotentiometer to get a OV5 reading, ora little more, on the multimeter. The"0V5' LED should just light; if itdoesn't, vary the potentiometerslightly until it lights. If the 'OV5' LEDlights when the multimeter readsmore than ±0V1 from OV5, then youmay have to change the value of R12.Increase it if the voltage is low,decrease it if the voltage is high. Justtake the next highest or next lowestresistor value; you're only after arough indication, after all.

Set the potentiometer fully 'up'(fully clockwise); if the battery is wellcharged, then the multimeter shouldread 13V5 or above and the '13V8'LED should turn on, along with the'12\i' LED. Now, reverse the AutoTester input leads. The POLARITY LEDshould come on.

If you can't get the properindications, check with the multimeterthat you are getting 7V5 (within ±0V3)across ZD1 when you press theVOLTS button. Also check thevoltages on pins 6, 9 and 12 of IC1when you press the VOLTS buttonand see they are close to those givenin the circuit description.

If all is well, proceed with testingthe OHMS mode. Disconnect the 12Vbattery, then set the multimeter toread resistance (should be the X1scale). Adjust the potentiometer untilthe multimeter reads about 100 ohms.Press the OHMS button and the '0-150' LED should come on. Turn thepotentiometer until that LED goes outand keep turning till the '10k' LEDturns on; it should turn on when themultimeter reads somewhere in thevicinity of 10k.

With the Auto Tester leads opencircuit, both the "10k" and '50k' LEDsshould turn on.

You are now ready for use. Happyfault-finding! HE

BY Fi Id)

4oL.I's -tut Rko-Cok-fRoUi)ciERtiL c_onric, ALotifi

(61) UV NrINI!).14 A Ef.wCALKS


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Square PCB Switch 65.

RUGBY ATOMIC CLOCKThis Z80 micro controlled clock/calenderreceives coded time data from NPL Rugby. Theclock never needs to be reset. The facilitiesinclude 8 independent alarms and for eachalarm there is a choice of melody or alternativelythese can be used.for electrical switching. Aseparate timer allows recording of up to 240 laptimes without interrupting the count. Expansionfacilities provided.

Ready Built Unit £1 45 + £5.00 carr.Reprint of ETI articles at E1.00 .+ s.a.e.

AS DESCRIBED INJUNE/JULY /AUGUST

ISSUE

MICROTRAINERComplete Kit £64.00 + £1.00 p&p8V 1.8A PSU £7.00 + 70p p&p1802 Ref. £7.00IDEAL for HOBBYISTS - learn andexplore the workings of microprocessorsand unravel the mystical field of computers.INVALUABLE for training centres, schoolsand industries - gives effective insight intomicros to engineers, electricians etc notdirectly involved in the computer field.INEXPENSIVE - a truly low cost teachingaid - in fact a short step towardsdeveloping new ideas and systems.

CA302845 120p M515161 5001,

MICRO COMPUTEROFFICIAL DEALER

Please phone tor availability

BBC Model B £399(Inc' VAT) Carr £8/unit

Model A to Model Bupgrade kit £50

Fitting charge £15

Individual upgrades also availableWORD PROCESSOR 'VIEW'

16k FROM £52TELETEXT ADAPTOR £195PRESTEL ADAPTOR £90

SECOND PROCESSOR 6502 £170SECOND PROCESSOR Z80 £290

ACORN SOFT/BBC SOFT/ GAMES PADDLES INSTOCK

TEctiNoNIATR:MAIL ORDERS TO: 17 BURNLEY ROAD, LONDON NW 10 lED

SHOPS AT: 17 BURNLEY ROAD, LONDON NW10(Tel: 01-452 1500, 01-450 6597. Telex: 922800)

305 EDGWARE ROAD, LONDON W2

32

FLOPPY DISC INTERFACEinc. 1.2 O.S. £95 + £20 installationBBC FLOPPY DISC DRIVESSingle drive 51/4" 100K £235 + f6 carr.

Dual drive 51/4" 800K £799 + f8 carr.BBC COMPATIBLE DRIVES

These are drives with TEAC FD50 mechanisand are complete with power supply

SINGLE: 100K £190; 200K £260; 400K f340

DUAL: 200K £360; 400K £490; 800K £610Drive Cables: Single £8 Dual £12

MICRO TIMERThe programmable clock/timer is a 6502 baseddedicated micro computer with memory and 4 digit7 segment displays to form an extremely versatiletiming device with following features 24 hour 7 day timer 4 completely independent switch outputs 6 digit 7 segment display output to indicate

real time turn-off times and reset times Individual outputs to day of week, switch and

status LEDs Data entry through a simple matrix pad

Further details on requestComplete Kit E56.00 1 11 00 p & pPSU £7.00 1 70p p & p

Construction details supplied

PLEASE ADD 40p p&p & 1507o VAT(Export: no VAT, p&p at Cost)

Orders from Government Depts. & Colleges etc. welcome.

Detailed Price List on request.Stock items are normally by return of post.


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50 IFETt FieldEffect transistorproiects

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52 PROJECTSUSING IC741 £1.25More than 50 waysof using theubiquitous IC741.

50 IFETI FIELDEFFECTTRANSISTORPROJECTS E1.75Contains a widerange of projects, all

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COUNTER DRIVERAND NUMERALDISPLAY PROJECTS£1.75Features many variedprojects usingnumeral displays.counter and driverICs.

CIRCUITSUSING IC's E1.35All you need to knowabout using IC's forAM or FM reception.

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PRACTICALCONSTRUCTION OFPRE -AMPS, TONECONTROLS, FILTERSAND ATTENUATORSE1.45Contains practicaldesigns for use with

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IC 555 PROJECTSE1.95The 555 timer users

CHOOSING ANDUSING YOUR HI-FIE1.65Concise informationfor all hi-fienthusiasts.

ELECTRONIC GAMESE1.75Amusing electronicgames which caneasily andinexpensively beConstructed by theenthusiast.

ELECTRONICHOUSEHOLDPROJECTS E 1.75Packed with circuitsfor projects that canbe used in or aroundthe home.

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ELECTRONIC MUSICPROJECTS E 1 .75Many practicalcircuits for lesscomplex items ofelectronic musicequipment.

ELECTRONIC TESTEQUIPMENTCONSTRUCTION£1.75How to build and usea wide range of testequipment for thehobbyist.

POWER SUPPLYPROJECTS ET .75Packed with circuitsfor building variouskinds of powersupply.

SINGLE ICPROJECTS E 1.50Easy to constructprojects basedaround a single IC.

PRACTICALCOMPUTEREXPERIMENTSE1.75Build and examine anumber of basiccomputer circuitelements.

ELECTRONICPROJECTS USINGSOLAR CELLS E1.95A range of practicalapplications usingsilicon solar cells.

VMOS PROJECTSE1.95Contains a number ofvaried and interestingprojects using VMOSpower FETs.

DIGITAL ICPROJECTS 1.95

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INTERNATIONALTRANSISTOREQUIVALENTSGUIDE E2.95Find possibleequivalents for apopular user -orientated selectionof modemtransistors.

HOW TO USE OP -AMPS E2.25All you need to knowabout Op -Amps, asource book ofcircuits and designcalculations.

AUDIO PROJECTSE1.95Clear information onhow to build pre -amps, mixers, poweramps, tone controlsetc.

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BBC/HEBOT InterfaceA complete kit of parts andcomponents for the project is beingsupplied for £24.00 by Kelan(Hobbyboard) Ltd., North Works,Hookstone Park, Harrogate, NorthYorkshire. The PCB is availableseparately from our PCB Service-seepage 71.

Aerial Without WingsA suitable toroid for this project isavailable from Neosid Small Orders1982, PO Box 86, Welwyn GardenCity, Herts AL7 1AS, for just £1.10,including P&P.

Stall ThiefThe 0.25" PCB -mounting push -onconnector blades used on theprototype are not absolutelynecessary, but they do give a firmer,more reliable connection. They are notstock items and will have to beordered specially; identification is easyif you quote the RS Components stocknumber -533-229. Alternatively, 0.1"PCB pins may be used, but make sureyour soldering is secure!

The relay is not crit.cal, as long as itis a 12V type, 200R coil with contactsrated at 5A or better; the open -contactgap should be wider than 5mm forreliable operation.

Component cost, excluding the PCB,relay and connector blades, should bearound £2.00.

Check ListRESISTORS(All V, watt 5% carbon)4 x 4k7; 2 x 1MR; 1 x 10M; 1 a 680k; 1 x 2M2; 1 x 330R;1 x 10k.

CAPACITORS1 x 100n; 1 a 10n; 1 x n; 1 x 4u7; 1 x 10u 16Velectrolytic.

SEMICONDUCTORS1 x CD40118; 2 x 1N4148; 2 x BC 108 or similar.

MISCELLANEOUS1 x 12V/200R relay, contacts rated 5A or better; PCB; 6x 0.25" connector blades or 0.1" PCB pins; optional case;wire, solder, nuts and bolts etc.

Auto -TestAll the components and parts for thisuseful project are stock by mostsuppliers-Greenweld Electronics, forexample. The cost ought to be under£3.00, excluding the case and PCB.

Check ListRESISTORS(All 5% carbon)1 x 47R; 1 x 180R; 1 x 82k; 1 x 100k; 2 x 410; 1 x 1k; 1 x

10k; 1 x 12k; 2 x 820R, 1 x 3k3; 3 x 150R; 1 x 100R.POTENTIOMETERS1 x 100k miniature trimpot.

SEMICONDUCTORS1 x LM324; 3 x 0.2" (5mm) LEDs; 3 x 1N4148 or similar;1 x BZY88C7V5; 1 x BZY88C15V.

MISCELLANEOUS2 x push -to -make switches; PCB; case; 52 x 30 x 100mmapprox; PP3 battery t clip; 2 x alligator clips and leads;wire, solder, nuts and bolts etc.

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TX1002Electronic Ignition Contactless or contact triggered Extended coil energy storage circuit Inductive Discharge Three positionchangeover switch Distributortriggerhead adaptors included Die castweatherproof case Clip -to -coil or remotemounting facility Fits majonty of 486 cyl12V neg. earth vehicles Over 145components to assemble.

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Feel like sounding off?Then write to the Editor stating your Point of View!

Audio AnalyserWe have received several queriesabout this project, which regrettablyhas had more than its fair share ofmistakes.

The entire file has been passedback to the designer with instructionsto sort it out, quickly. Meanwhile, weask all readers who've had a problemwith this project to be patient - it willbe unravelled. One problem withelectronics is that components canvary quite widely from their paperspecification, and because of this,individual prototypes can workperfectly, when 99% of other modelsbuilt to the same design will fail towork properly (or at all); conversely,sometimes a model which has beenbuilt perfectly with all the propercomponents will be the 1% which willnever work until half the componentshave been changed . . . the electron isstill a mysterious animal, despite theconfidence with which we shunt itaround.

Apropos of that, let me add that theTelephone Timer (HE June/July '82),which has turned a few hairs grey, isunder similar surveillance, but atpresent we are not sure where theauthor is. . . On a more minor note,we are looking again at Big Ear (HEDecember '82) to find out why a fewpeople have had minor but persistentproblems with it. We haven'tabandoned you, and the answer willeventually appear. Now on with theshow . . .

Missing DesignerIs Mr. Peter Walton, who sent us aSelective Caller project a few monthsago, out there? We would like a wordwith him, but don't have his address.Please write.

Alarm AlarmDear Sir,I am building your Low Cost Alarmsystem, from HE December '82. I haveall the parts for the alarm, but I do nothave PBCs and the window foil andterminals. If you do not have thesecomponents I would like to knowwhere I can get them.Yours faithfully,Stephen Herron,Newtownabbey,Co. Antrim,N. Ireland.

Up until now there has not been amade-up PCB available for the LowCost Alarm; but there is now. See thePCB Service page in this issue. We

don't of course stock components ofany kind (not now, not ever, never -we have enough trouble with ETIstealing our personal store but thefoils and switches for this project are,of course, available from the sourcementioned in Buylines: in this case,Maplin Electronics.

Siren CallDear Sir,Project: Low Cost Alarm system, HEDecember '82.

1) AWD. Greenweld (1982/3catalogue) do not seem to supply thesiren as described in the text, partslist and photo.

Could you please suggest an altera-tive supplier, and full specification, ifpossible? (This AWD sounds verygood, with a warbling tone, onlyOmA75,95dB at 1 m, and verycompact, as per photo.)

2) PCB. Is this going to be available?Many thanks,Dr. K.D.E. Whiting,Hatfield,Herts.

This AWD is on the RS componentscatalogue as 249-413 - ask yourlocal dealer to order it for you. As forthe PCB, it's now available, as fromthis month.

Projects From The PastDear Sir or Madam,I have two problems I wish you couldsolve for me:

1) HE September '79 page 23Starburst. I bought your ETI Printmade PCB, fitted components, wiredup, tested and got no result. The ICsare working, and so are the LEDs(tested before wiring boardstogether, ie LEDs). Somebody made ahash of component layout on page 26,they even managed to get the powersupplies back to front. Did they makea mistake in values for R7 to R11?

2) HE October '81 Pages 51 and 52Touch Lamp. As is my practice, I amtrying to fit this lot into a small box,could you tell me what relay youused, name and shop or agent?Yours faithfully,V. Hogg,Hayes,Middx.

Yes, the OV and +9V notation shouldbe swapped around on the PCB layouton page 26 - an easily -spotted error.

The values for R7 to R11 shouldproduce reliable switching providedyou are using the specified transistor.However, if you think this is the

source of the problem, reduce thevalues to around 18k (don't go lowerthan 10k).

A relay was not specified for theTouch Switch but any 6 to 12V, 100Rcoil relay with single changeovercontacts rated at 10A or so will suit;just be careful with the counting andwiring. Such relays are available fromalmost any mail order supplieradvertising in HE.

This also seems a good time toremind all our readers that technicalenquiries such as this one cannot beanswered personally unless an SAE isenclosed, and although we try to beprompt, especially with enquiriesabout projects under construction,your Hobby Electronics has to comefirst - so you may have a long wait.But don't feel you are alone -designers have all the problemsconstructors have, and then some . .

Shed A Little Light

Dear Sir,I have been working on a light sensitiveswitch project based on one of yourcircuits but have a problem withoperation during daylight.

I want the switch to operate onartificial light, eg car head -lights, but notdaylight. Is there a light sensitivecomponent suitable and if so where canit be obtained?F S Roberton,Kelso,Scotland.

You could attack this problem in one ofthree ways: a you could mount yourlight receptor in a recess or cowling sothat it would get a minimum of normaldaylight but would pick up a headlightbeam pointed at it b) you could use alogic circuit of some kind which wouldpick up a simple pattern of flashes fromthe headlights c you could opt for acommercial infra -red or ultra -sonicremote control and sensor combination- which would do the job, but is ofcourse a completely different solutionfrom using a light-sensitive switch.

We don't know of any light receptorwhich will distinguish betweenheadlights and daylight without the kindof help described here. Does anybodyelse have any suggestions?

Not Beaten Yet

Dear Sir,In HE December '81 you had a DIYDrum Synthesiser. Have you any of theaforementioned drum synth circuitboards left, and if so could you pleasequote me a price?


S Hallam,Horsley Woodhouse,Derbyshire.

All our projects are DIY unless you cancon a friend or relation in building themfor you! Perhaps one day we'll design arobot that builds itself . . .

Unfortunately we don't do a PCB forthe drum synth, but you can trycontacting Bewbush Audio, 26Hastings Road, Pound Hill, Crawley,Sussex and asking for information.

Getting Into Phase

Dear Sir,Could you please send me your latestprice list and catalogue on the HE PhaseOne unit and any other musical effects.A Brandon,Wins ford,Cheshire.

I think you mean Phase Four, the HEPhaser Unit. If not, you're in the wrongstore! There is no kit for Phase Four, butthe PCB is still available from our PCBService. For other effects, consult theCumulative Index in HE January '83 -we can always supply back issues orcopy articles of old projects, but we canonly supply the PCBs as listed in themost recent issue, ie this one. Any help?Phase Four, for anyone else who wantsto check it out, is in HE December '82,and features a custom -designed casesupplied by Newrad Instruments.

TimeTo Switch On

Dear Sir,AS a regular reader of HE, I wonder ifyou could publish a timer project forswitching mains appliances on and off.The application I have in mind is toswitch my hi-fi on to record a certainradio programme while I'm out. Whenthe programme is over, the timershould also switch the system off. Arepeat function for recording the sameprogramme each day (holidays, etc.)would also be useful, and a smart caseand digital display would make the unitfit in well with hi-fi equipment, etc.

Great mag, keep up the good work.J. Jezard,Tonbridge,Kent.

There are a number of timers alreadyon the market which will switch amains socket on and off at presettimes. However, these are relativelyexpensive and do not include the extrafacilities you mention. So we havestarted work on a design for such atimer and hope to publish one in thefuture. In the meantime, you might liketo take a look at your central heatingswitch - some have an external mainsoutlet socket which is switched on andoff with the heating. Of course, you'dhave to switch off the heating systemfirst to avoid wasting energy bywarming an empty house!

Raiders Of The LostHobby . . .

Dear Sirs,Having been a keen reader of HE forsome time I have noticed how backnumbers of the magazine soon becomeobjects of great demand among friendsand colleagues, and this leads topermanent gaps in one's collection! I amin fact in need of issues from Novemberand December 1980 and February1981 or more specifically the excellentarticles in the series on DigitalElectronics by Ian Sinclair.

Could you please advise me how toobtain these if they are still available?J P Sheppard,Cheltenham,Gloucestershire.

Yes indeed. Shall I refer this reader onceagain to our Backnumbers page, "not inevery Hobby, but in most of them"? Wecan't always supply the wholemagazine, glossy cover and all, but wecan always supply copies of the articles.

Another award -winning idea!Introduce your friends and colleagues toour Backnumbers page. And ourCumulative Index (HE January '83).Then they can see not only what they'vebeen missing, but how to get theirhands on it without raiding yourcollection . . .

Batteries In The Breeze

Dear Sir,I have been an avid reader of yourmagazine for some months. InNovember !leave for Kimball which is inthe Pacific. For some time now I havebeen trying to find out how I can use anormal car alternator driven by a form ofwindmill to top up a 12 V storagebattery during the day and possibly runlimited lighting at night.

I would be grateful if you could helpme on this subject in any way.M J Maddison,Cleethorps,S. Humberside.

This is essentially a mechanical problemwhich we can't really advise on but thebasic answer is something like this:bearing in mind that car alternators arenegatively earthed, if you can take thenegative line from the metalwork of thealternator, or whatever it is mounted on,and the positive from one of the largertags on the back of the unit, you canconnect up the battery.

You will then have to calculate howfast the alternator needs to turn tocharge the battery. A tickover speed, ina normal car engine, the alternator willonly just be charging the battery, if atall. You can calculate the tickover speedof the alternator by physically measuringthe diameter of the pulley wheel on thealternator, and the one one the engine,divinding the engine pulley by thealternator pulley and multiplying the lotby the number of revs per minute atwhich the car engine ticks over. Thentriple this figure and you will have the

RPM needed from the alternator tocharge the battery at a reasonable rate.

The alternator can be driven by asimple pulley and belt drive straight fromthe wind vane, but the gear ratiobetween the pulleys will have to be suchthat the alternator is not turning tooslowly to charge, or so fast that the actof charging slows down the windvaneto the point of uselessness.

You would have to discover this byexperimentation, as much depends onthe speed and strength of the wind. It isbest if you use the battery for theexperimenting, with an ammeter on it toshow how fast (or not) it is charging.

Into Electronics - Minus!

Dear Sir,I would be obliged if you could let meknow if you have a copy of 'IntoElectronics Plus' from 1979, and if sothe price.K Edwards,Barrow -in -Furnace,Cumbria.

Sorry! IEP really is out of print now.However, if you're eager, you couldconsult our wonderful Cumulative Index(HE January '83) and obtain copies ofall the Into Electronics articles. See theBacknumbers page for furtherdetails . . .

Microtrainer Manual

Dear Sir,Ref: Hobby Electronics Vol. 4, No. 6,June 1982: HE Microtrainer, page 62.In the above article you refer to RCA's'User Manual for the CDP1802COSMAC Microprocessor'. Can yousupply me with the address to write tofor this publication, please? Yourassistance would be much appreciated.Many thanks.P V Haviland,Lichfield,Staffs.

The supplier of this manual at the timewas none other than Technomatic Ltd.,of 17 Burnley Rd., London NW10 1ED,who supplied the HE Microtrainer. Trythem.

Component Copies

Dear HE,I would like to know how much it wouldcost to obtain photocopies of yourseries of articles 'Into ElectronicComponents, which I think started inAugust '81. I would like to know thecost of the whole series except for parts8 and 9.C K Williams,Bracknell,Berks.

'Into Electronic Components' did indeedbegin in HE August '81. As for copies, ifyou inspect page 68 of this issue,you'll find our Backnumbers service. Ifthe back issue isn't available, we cansupply a photocopy; they like theBacknumbers, cost 1.25 each. HE


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Firtill

As the month of May rolls around again Clever Dick,who is himself usually quite merry, is rolling around, still.

The CD I -Spy award of the monthgoes to an observant reader inGlasgow. And who said there are nomore surprises in the world?

Dear CD,First of all, this is a neatly written,amusing, original letter (November,page 53).

I have written to help you with yourmaterial problem (you mean you didn'tknow you have a material problem?)!I refer, of course, to the letter fromD.C. Holmes (September page 31 ANDNovember page 21) and the letterfrom R. Einstein (November page 53AND December page 51). Is there anyreason for this? Perhaps they arerelatives of someone in the HEoffices?

Although I considered writing to theeditor about his Points of View, whereone duplicate appeared, he seems togive out very few (none) of thosefamous blue and gold delights that arethe dream of every HE reader.

I like HE very much, but how aboutmore Veroboard projects? Keep up thegood work.Steve Morton,Glasgow.PS Any reader following this letterwithout the aid of the issuesmentioned may wonder what I'mgoing on about.

At first I wondered what you weregoing on about, too . .. but yourreport is entirely accurate. Thoseletters were duplicated, much to oureditor's horror. When I mentioned it tohim he put his head in his hands andsobbed loudly for two minutes (hedoes this at least once a day), thenpromised to look into it. In themeantime one of those fabled "blueand gold delights" is winging its waytowards you courtesy of the editor andHigh Speed British Post.

And who said the age of miracleswas past?

Since we have been presentingmore practical projects in HE, we haveadopted a policy of putting mostprojects on PCB, since this makesconstruction much more reliable and,in general,.PCB layouts are not asvulnerable to the dreaded 'gremlins'.However, projects will continue to bedeveloped on Veroboard where thismedium is appropriate - that is, nottoo complicated and difficult tobuild up correctly.

Now here's a man with a problem orthree....

Dear Clever Dick,I have been taking your excellentmagazine for a number of years andalthough electronics is a subject / findfascinating, I have never tried buildingone of your projects. However,necessity seems to be driving me todo so. Let me explain.

Since I have lived at my presentaddress about twelve years, I havesuspected that the television signalfrom the Mendip hills is somewhatweak, due to the position of a hillbetween it and me. However, I havebeen able to run three monochromeTV sets reasonably well off threeseparate aerials on the roof. Thepictures have been a bit snowy, butnot too bad.

Last week I thought I'd spoil myselfand buy a colour portable set for thebedroom, but when I got it home itwould not work on its own set -topaerial. When connected to one of therooftop aerials it worked, but hardlysatisfactorily. So, / removed one of myaerials from the roof and connected itby a short lead directly to the set,pointing the aerial out the window inthe direction of the transmitter. Thisproduced the best picture yet.

From the above experiments Iconclude that the signal is very weakindeed and that the long lead is verynoisy, so I have a poor signal-to-noiseratio, as it were. I propose to build theTV Masthead Amplifier (February '82issue) and put up a higher mast also,but all this raises a few questions inmy mind.

If I put up two aerials side by side,and connect them together, will thisimprove my signal-to-noise ratio?

Will the Masthead Amplifier drivefour TV sets, or can the output fromone amp be fed to the input ofanother?

Can I simply join the serialstogether by soldering the inner wirestogether, and the outer braidstogether? If not, what is the best wayto runs three sets from one lead?

The Masthead Amp is said toamplify the signal by 18 times and torun from any voltage between 10Vand 24V; does it give best amplifica-tion on the higher voltage?

Is it worth making a power supply?If not, what batteries would yousuggest? What is the currentconsumption?

Can you suggest a book that would

explain about fitting aerials?Since my colour set isn't yet

working, do I need a colour license?What's a binder?

G.H. Wakefield,Weston -super -Mare.PS The hill that weakens my signal iscalled Bleadon Hill. I think the nameis quite fitting, don't you?

If you pronounce the words "BleadonHill" slightly differently, it alsodescribes my reaction to this letter,which raises a few questions in mymind, too. Like, why does he needfour TV sets, for example? Nevermind, some questions are better notanswered (ignorance is quite pleasant)and I suspect this is one of them.

Yes, you can connect two aerialsside by side (better one on top of theother), provided they are accuratelypositioned and linked by what iscalled a 'phasing harness'. Theprecise positioning of the aerials andthe matching harness are both toensure that the signals are in phaseso that they add, rather than subtract.

If you are determined to run four TVsets you can do so from a singleaerial using a suitable distributionsystem. Rather than the methods youpropose (you can't simply connectaerials together and hope for the best)you can use four separate MastheadAmplifiers connected to the one aerialby appropriate impedance matchingtransformers.

The amplification provided by the0M355 device, which is at the heartof the Masthead Amplifier, isdependent on the supply voltage andthe gain will be higher (27dB) at 24Vthan at 1 2V (23dB). Typically, thedevice will draw about 35mA from thesupply and if you really do want fourof them (I) you may as well build a24VDC power supply capable ofsupplying around half an amp or so.

A suitable book, which will answerall your questions in detail, is "LongDistance Television Reception (TV -DX)For the Enthusiast" by Roger W.Bunney. It is published by BernardBabani (Publishing) Ltd. and isavailable through the HobbyElectronics Bookshelf. The principlesof long-distance reception are equallyapplicable to fringe area reception.

Finally, I cannot comment on yourlegal position but if you need informa-tion on this or further answers to yourten thousand questions, contact theEngineering Information Service,Broadcasting House, London W1A1 AA. HE


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Into Radio U

RADIORULESHelen Armstrong

Just one more step before youlaunch into space-the RadioAmateur's Examination!By the time you read this you should,thanks to Radio Rules, be well on yourway to being your own radio expert,which means that you will be nearlyready to face the final hurdle inbecoming a radio amateur - the RadioAmateur's Examination, better knownas the RAE.

Radio amateurs have a far widerchoice of wavebands, and far morerange and power to play around with,than CBers (who, until recently, weren'teven legal) and the idea that members ofthe public should be allowed to transmitanything at all without a mass of officialcontrols is a very recent one in the UK.CB radio has been around in some othercountries, notably the USA, for a longtime. But even in these places, theamateur has to pay for his greaterfreedom in what and where hetransmits by proving that he or she iscapable of running a station withoutinterfering with other transmissions. Soradio amateurs have to pass a fairlydemanding exam.

The original justification for licensingamateurs to transmit was to encouragethem to train themselves as radiotechnicians and operators in case theywere needed in times of emergency orwar, and the license states to this daythat an amateur radio station is 'part ofthe self -training of the Licensee incommunication by wireless telegraphy'.This is also a tribute to the develop -

For information about the RAE, youshould contact the Home OfficeAmateur Radio LicencingDivision, Waterloo Bridge House,Waterloo Rd., London SE1 8UAfor a free copy of their booklet Howto Become A Radio Amateur, whichwill tell you the up to date licenceconditions along with a lot of otheruseful information. For full detailsof the exam, and sample questions,write to the City and Guilds ofLondon Institute (who actually runthe exam) at 76 Portland Place,London WC1 N 4AA.

To get hold of the RadioAmateurs' Examination Manual,which contains all (or most of) the

ment work done on radio by amateursin its early days, as you will doubtlessremember from "The Birth of Broad-casting" (HE February '83).

Amateur radio is more a pastime forpeople who are interested in radio andits whys and wherefores, than for thosewho simply want to communicate withfriends without finding a callbox. Thatsaid, the RAE, although it aims toestablish that the would-be amateur iscompetent to operate a station, is astraightforward examination for anyonereasonably familiar with the subject.The change, three years ago, fromstraight essay -type examination tomultiple-choice questions has, despiteinitial grumbles and teething troubles,produced much the same percentage ofpasses as before.

This has sometimes led to complaintsfrom the old school that today'samateurs can hardly hold a screwdriver,let alone construct their own trans-ceivers - but amateur radio is morelikely to encourage a lively interest inradio if people can enter it at a levelwhere, once they understand theprinciples and can keep their hardwareproperly tuned, they can get out on theairwaves and learn the rest 'live'.Indeed, the arrival of CB, far fromrendering the amateur obsolete as hadbeen glumly forecast in some quarters,has given more people than ever a tasteof radio; as CB is very limited, many of

Finding Outtechnical background and informa-tion needed to take the extra(although it ought to be used as abasis for wider study if you aregoing to master the subjectproperly, and not just as the solesource), contact the Radio Societyof Great Britain at Alma House,Cranbourne Rd., Potter's Bar,Herts EN6 3JW, tel. (0707)59015. They will also take applica-tions to sit the RAE. The exams areusually held twice a year, in Mayand December, but there have beenso many applications that theremay be three sittings in 1983.Membership of the RSGB currentlystands at around 38,000 after

these then go on to extend their know-ledge and mastery of radio and becomeamateurs - the number of peoplesitting the RAE and joining the RadioSociety of Great Britain (RSGB) isincreasing dramatically year by year.

Terms and ConditionsBut it's not enough to know about radio.The first part of the RAE deals with theconditions governing amateur radiolicenses, and if you fail this, you failcompletely. You have to know the rulesbefore you'll be let loose. Althoughphrased in legalistic lingo which may bepuzzling even to people used to readingparagraphs of equations, the radio rulesare fairly straightforward and largely amatter of commonsense.

Cast your mind back to the first part of"Radio Rules" back in HE April '82, andyou will recall that Amateur License A isthe full radio licence which allows youto use amateur bands below 144MHz,as well as those above, and to transmitMorse Code (CW). Not many people optfor Morse now. A separate Post Officeexamination has to be taken for this.Most amateurs hold Licence B.

Your transmitter, receiver, test equip-ment and log are in fact a radio station,which is licensed to be set uppermanently at a named address, or inany other 'temporary location'; longer -term removals have to be notified as

rising a lot in the last five years.They publish a monthly magazine,will help members with technicalqueries and publish a range ofuseful textbooks which are, ofcourse, cheaper to members thannon-members. You don't have to bea member to take the RAE, but itpays somebody starting out in thehobby to be in touch with the mainmeeting -point for amateurs.

The RAE is like most other exams- to pass it, you learn the radiorules. Once you have passed andbeen certified safe to be let out onyour own, the door is open to thereal spirit of amateur radio.


Into Radio'alternative premises'. The station canbe operated by a pedestrian (colloquiallyknown as portable operation) or from aprivate vehicle (colloquially andofficially known as mobile operation -although I have yet to see one beingoperated from a bicycle, and operatorsusing a hand-held mike while drivinghave occasionally been stopped by thepolice for illegally driving with onehand!). Mobile operation is increasinglypopular, and there are manytransceivers and aerials designedspecifically for use from a car.

You must not, however, use thestation in a sea -going area (at sea or inan estuary, dock or harbour) or from anaircraft or public transport vehicle(although special aircraft and mobilelicenses are obtainable whereappropriate).

Section 1 of the license states thatyou are licensed to send in radio tele-graphy (which covers both voice trans-missions and Morse, although voicetransmissions are also called telephony)personal messages in plain languageabout things in which you or yourcontact are personally involved, but youmay not discuss business or exchangemessages on anyone else's behalf. Thisis designed to prevent the amateurbands from being used for commerceor propaganda rather than stop you fromsending greetings on behalf of a friend.The RAE Manual's section on operatingprocedures states "It should be a goldenrule never to discuss religion, politics orany other matter which may offend theperson to whom one is talking or anyonewho may be listening" - but this is onlya guideline, not, as some people think, astatement of law. You are definitely notallowed to transmit "grossly offensive,indecent or obscene" messages,however.

License the also permits the trans-mission of facsimile signals (radio -encoded pictures), radio teleprintersignals, video (amateur television) andtest and other signals relating directly tothese and not in any secret code. Thisdoesn't of course preclude the 'codes'and abbreviations once common inradio, especially in Morse, where theywere used for the sake of brevity andextra clarity, and especially to getaround any language barriers in inter-national calls.

Emergency ServicesAmateur operators may be (and oftenare) called out to help the police orother emergency services. In parts ofthe country groups exist which prac-tice working as a team or network-thisis known as a Raynet group-and theyhold communications exercises as wellas taking part in real emergency work.

Generally the only person permittedto use a station was the license -holderor another licensee under his super-vision. Now a pre-war custom, thesending of greetings messages by non -licensed people under occasional con-ditions, is being revived after long agita-tion by the RSGB, but this has not yetbeen incorporated in the licensingrules.

QSL cards are exchanged by amateursas a record of contacts made. Thesetwo are from Yugoslavia and Mallorca,with their national code letters.

Transmission by anyone using a falselicense number is likely to be promptlyspotted and reported by another station!No kind of recording may be transmittedexcept for certain test messages andtones, and nothing that infringes copy-right (which means, in effect, anythingpublished, or otherwise copyrighted) oranything misleading - jokes on the airare alright, but not if they could remotelybe mistaken for a distress call.

It's also a requirement of the licensethat you should be able to receive on thesame wavebands on which you aretransmitting, so that messages can bereturned. On the other hand, listening into the wrong thing is out: under Section5 of the Wireless Telegraphy Act, it is anoffence to deliberately receiveunauthorised messages, and disclosinganything about them to 'unauthorisedpersons' is an offense under theOfficial Secrets Act. This includes policetransmissions, so don't tell me your hifiamplifier picks them up!

Some of the most important licenseconditions concern the prevention ofinterference and keeping broadcastswithin the right frequency bands.Section 3 states that a satisfactorymethod of frequency stabilisation mustbe used, and that there must be equip-ment on hand capable of checking thatthe station is operating correctly. AndSection 4 makes it clear that themaintenance of the radio and morseequipment in a state which doesn'tinterfere with other transmissions is anabsolute requirement of the license, notjust a social duty. The Notes to thelicense give examples of when aerialsmay give rise to interference, or(another kind of interference entirely)when they may be in danger of foulingaircraft, or power lines, and the limita-tions imposed.

Sections 10, 11 and the footnotes saythat the station must be available forinspection at all reasonable times, andthat it can be closed down at any time.This is normally only done in a case of

national emergency, but the licenseitself can be revoked (and the operatorprosecuted) if the terms of the licenseare broken.

To further aid keeping track of trans-missions, you must keep a detailed logof calls and contacts made. Thiscomprises, basically, the date of the call,opening and closing of operation andthe address of any temporary premises(or the geographical location, for mobileoperation), the times, frequencies andcall -signs of each contact made andclasses of emission, including thoseused for CQ and test calls. The log mustbe signed by any other amateur usingthe station.

Signing OnThe license is specific about the use of acallsign. It must be broadcast at thebeginning and end of each period ofsending, and every 15 minutesotherwise. Extra identification letters

Safety inDon't give a new meaning to the oldexpression 'over and out'! Consultthe Radio Society of Great Britain'ssafety recommendations foramateur radio stations. A seriousamateur radio station usuallyconsists of several pieces of equip-ment, very often in various stagesof construction, modification,testing or repair. Any piece ofelectrical equipment carries somedanger from electric shock, butdoubly so when it's beingconnected and re -connected.Following this comprehensive listof safety precautions willeffectively remove the danger ofserious shocks. Here is a summaryof them:

Equipment should be turned onand off from one master switch;everything should be connected toa good, tested earth (not, asformerly, a water mains, as manynow have plastic sections; wireand terminals should be thoroughlyinsulated (there is often a tempta-tion to leave temporary terminalsopen and live); capacitors of morethan 0.01 uF (100n) should have ableeder resistor across theirterminals that will ensure rapiddischarge; capacitors with lowleakage should be stored with theirterminals short-circuited, as theycan otherwise build up a staticcharge (you can get a serious shockfrom a large capacitor) and better,capacitors in use should be dis-charged with a 'wandering earthlead', an insulated lead with somebare strands at the end, connectedto a permanent earth; all equip-ment should have conspicuousindicator lamps to show that it islive (apart from the safety factor, itdoes equipment no good of leave itswitched on when not in use andunattended); double -poledswitches should be used for


Into Radio are prescribed for mobile, temporary orpedestrian use, and for the main geo-graphical areas of the British Isles -GW for Wales, GM for Scotland, and soon. At a temporary location, a briefaddress must be included.

Probably the most familiar aspect ofnon -broadcast radio to people whoknow nothing at all about it is the'phonetic alphabet', where letters of thealphabet are replaced by distinctivewords beginning with the same letter.The alphabet published by the RSGB isrecommended rather than prescribed,and there are common variants, but theexaminers will want the versionspublished! The phonetic alphabet isused to make important messagesclearer in bad reception conditions, andit's generally better if you can stick towell-known versions, otherwise thepoint is lost. In any case, it's stated thatthe words used must not be "objectionalor facetious". The alphabet as given inthe Radio Regulations, Geneva, 1976, is

le Shackswitching mains on and off, and thecorrect fuses should be installed onthe equipment side of the switches.

A mains circuit breaker, such as amicro -switch, should be used toswitch off metal -cased equipmentautomatically when the lid or otherservice hatch is opened; test probesand lamps should be insulated; arubber mat should be used on thefloor if the floor is at all damp.

Equipment should be switchedoff before adjusting, and insulatedtools used. If any adjustments mustbe made while the gear is live, onehand only should be used, and theother hand kept in a pocket; head-phones should never be worn whileadjusting live equipment, andmetal -cased gear like microphonesand morse keys need to be properlyearthed; meters with metal adjust-ment screws are not safe to use onhigh -voltage equipment.

A check needs to be kept forunexpected live projections fromequipment, especially where metalscrews are used on control knobs;aerials should never be connectedto the mains or any other highvoltage source; where they areconnected through a capacitor, anRF choke should be provided.

The full recommendations aregiven in detail in the RAE Manual.

13EFISTIESI

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QSL cards from Poland and France.

printed in the footnotes to the license.Sections 12, 13 and 14 and 15

summarise the terms under which thelicense is issued, the most importantbeing that the licensee shall pay upevery year, and that the terms of thelicense may be a varied by the Secretaryof State in a general announcement inthe press or via the BBC.

Section 16c and the following notescontain information about how the restof the rules should be interpreted andvarious other important information,such as the correspondence address atthe Home Office. It also harks back toSection 2, which briefly draws ourattention to the fact that radio rulesare international, in effect, whateverthe local variations. It refers to theInternational TelecommunicationsConvention of 1973 and various othersets of international regulations. TheGovernment in its turn has to abide byradio rules when broadcasting at homeor overseas.

Practical ProcedureApart from the Home Office licenseconditions, the RSGB issues its ownadvice for operators as to properoperating procedure, to ensure clearand trouble -free communication.

Quite a large chunk of the advice is forMorse operators, including a detailedlist of 'Q' codes, and calling patterns forestablishing a contact, making, andending a transmission, and an RST codetable, giving the standard notations fordescribing the quality of a transmission.The use of the Q and RST codes, as wellas the phonetic alphabet, has spilledover into voice radio. The originalpurpose of codes was to increase boththe brevity and the clarity of trans-missions, but brevity is not generallyimportant in voice radio and the use ofabbreviations has become more amatter of jargon than necessity.

Amateur jargon can be quite incom-prehensible to the non -initiated(although never as colourful andobscure as CB jargon). The RSGB is

tending to discourage the use of jargonand CW codes, but it would be a pity ifjargon disappeared altogether as theuse of patter is one of the charms ofradio.

Contacting other StationsWhen trying to establish a contact withanother station - known as 'calling'-it is important to get your call out asquickly and as clearly as possible. Givethe callsign of the station you are callingonce or twice, depending on conditions,and then your own callsign at leasttwice, using the phonetic alphabet. Ifthere is no response from the stationyou are calling, call again, putting theemphasis on your own callsign, butdon't keep calling continuously. Leave ittill later or (if you are mobile) until youare closer to the station.

Likewise, CO (general) calls can berepeated several times, giving your call -sign clearly, but no information isneeded other than 'calling and stand-ing by', and you should listen for afew moments between each call. Don'tkeep on and on calling CQ on the samechannel if you get no response in areasonable time - either listen aroundto see if another exchange is about tofinish, or try another channel.

Once the contact is made, the stationsshould spell out their callsigns until theyare sure that both have been receivedcorrectly. After that, callsigns only needto be given every f ifteen minutes, so thatin good operating conditions a normaltelephone -style conversation can beheld; if reception is down a bit the words'break' or 'over' give an additional signalwhen one operator has finished talking.Give both callsigns again in phoneticalphabet when signing off; this alsohelps other stations listening in, whomay wish to call.

Incidentally, if you have troubleremembering callsigns, write yourcontact's callsign down at the beginningof the exchange if you can; this saves arepeated 'What was your callsignagain?' and 'G3 Yankee what was it?'every time callsigns are exchanged,which is all too common.

When transmitting to a group or 'net'give your callsign at the beginning ofeach transmission, to let the group andother listeners know who is talking. Youcan also pass the call on to the nextperson to speak, if you are taking turns.

It is not necessary to continually listthe other callsigns in the group, butsome groups have the practice of lettingone member act as 'master ofceremonies', repeating the callsignwhen one member has finished andpassing the call on to another memberof the group.

It is helpful also to say briefly whatyou are about to do if you are changingchannel, have just arrived on a channelor are signing off for the time being.

An important part of any exchange,especially long distance ones, wherethe signal strength of either operator islikely to be below maximum, is to give asignal strength report. In CW, a codeknown as the RST code (readability/signal strength/tone) is used. There are


Into Radiofive levels of readability, from unread-able to perfectly readable, and ninelevels each for signal strength and tonefrom one to nine. For operatingproficiency certificates and awardsgiven by the RSGB the minimum signalreport needed is RST339, or RS33,which are the minimum practicalsignals.

In other parts of the world, sections ofthe amateur bands are reserved forcertain classes of operator usingparticular modes of transmission (egCW or radio teleprinter (RTTY). There, itis illegal to fail to observe theserestrictions; not so from the UK, but weshould still adhere to them at all timesas a courtesy - this is only commonsense, as are most of the rules ofprocedure.

It is only common sense not toattempt to call a station which is clearlytrying to establish a call elsewhere, forinstance, no matter how badly you wantto make a contact with a station in thatparticular location; not to call CQcontinuously if you are getting no reply;not to interrupt an establishedexchange; not to hold conversations onchannels such as S20 (145.5MHz)which are so normally used for calling.

If you contact somebody on a

channel which he has been working,move off again once the exchange isfinished; don't use long-distance bands(DX) for local calls while they are openfor long-distance communication, andwhen conditions are unusually good forlong-distance contacts, keep your callsshort - there will be queues of otheroperators hoping to pick up some rareQSL cards, waiting to speak to the samestations you are speaking to.

Repeaters and SatellitesOver the last ten years, a number ofunmanned transceivers, mounted onmasts at high geographical points, have

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QSL cards from Finland and the USSR.

been set up. These receive VHF or UHFtransmissions from portable or mobilestations on an input channel and re-transmit them on a different outputfrequency within the same band, butwith greater power. Thus the range oflow -powered equipment can be doubledor better.

These relay stations are known asrepeaters and have their own call signs(eg GB3PI near Peterborough, the'Cambridge repeater', one of the first tobe opened). They can more than doublethe range of low -powered equipmentwithout the use of extra power or betteraerials. To prevent continuousoperation of the repeater by one caller,or when not in use, the repeater isusually designed to be switched on andoff remotely: on by means of a 1750Hztone (toneburst) transmitted by thecaller, or by the user's carrier on the

input channel at the beginning of eachtransmission, and off automaticallyafter, say, one minute - a limit knownas 'time out'.

Repeaters only respond to anaccurate FM signal and if the accessingsignal becomes inadequate, therepeater will switch itself off. After eachover, the repeater will wait for a minuteor two, and then broadcast a signal inMorse to show that it is free for use.

There are also satellites for amateuruse which play a similar role torepeaters, only at a greater power andover a longer distance. The first one waslaunched in 1961 and others have goneup periodically since. They are known asOSCARs (for Orbiting Satellite CarryingAmateur Radio), each with its own owncode number. They are transponders,which accept single sideband, radioteleprinter or Morse signals (forpreference, although any mode isacceptable) over certain wavebands,and retransmit them on another band.At the moment they can transpond from432 to 144MHz, 144 to 432MHz and144 to 28MHz. Unlike repeaters, thesatellites are continuously operationaland require no special signal to accessthem.

To transmit to the satellites, a powerlevel of 80 to 100W ERP is needed,normally provided by a transmitter of 10to 15W output with antenna gain of10dB, and the antenna must be in line ofsight with the transmitter and, for bestresults, capable of following it.

Alright on the NightThere are a number of ways to learnenough about radio to take the RadioAmateurs Examination successfully.The only essential rules are: know whatis in the syllabus (it helps to be familiarwith the Radio Amateur's ExaminationManual), and make sure you both learnthe theory and get as much practical

Below: a set of RAE -style papers. Samples can be obtained from the Home Office.

PAPER 1

al the same day

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cl ten days

d) one month

An amateur sending end reran ing statrop for wireless tebgrav yrr,ay knee

31The amateur's Ircence and log book it liable to ...fon Sv

al a person acting under the authority atthe Secretary al State at any reasonable time

01 a person acting under the authority of dmSevetary of State at any time

cl *Morals ol the Radio Society of cartBritton at any. reasonable time

d1 the lecel police, on receipt of complaints,at any time

irelus Potion may M "'"d includes IM use oI the

,1 erne ssaPi nn plain lenwaP which are emends of a buttress nature provid'M fMa '"

isbl any third party messages which may appear

necessary 'm times oI national

dl .lailidpedarnmg to the commercial equipmentusd by the operating station

a)England, Ireland, 5.tlan6 and Wales.

hi England, Northern Ireland, Scotland and Wales

cl th,ejr=donr of Great Brit.. NorthernIreland,. Isle al Man a. the

Channel

di Me Unit. Kingdom of Gast Ordain andNorthern Ireland

44

51 The ...urn bandwidth for J3E transmissions rs chosen so as toi

a) not exceed 25 kHz

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dl not exceed 1/25 m of the frequency Semi barns us.

'""""'p r ""'"

al 1. Patron owner

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dl the owner of the power cable

61 Particolar care will havewhen woe!s are pted

to be taken to mrnimrse the trak of interference to others

a) in 8. loft

bl close to overhead power lines

c) .S than Mr above the ground

al wrthrn.yds of an aeroplane boundary

91 To reduce nouns borne interference when ming an end -fed antenna one must ensurethat:

al the mains eatrn is used

bl a go.. short lawresotarde °enema. to a cold water tap d used

cl no earth connection is used

dl a good, Nat low resotence connection to an earth spike is used

101 ZTOV:7td'LZ.7pn=;'"""'"'"'al aeal.1

soned

bl horn time to time

c) on the receipt al .). eguipm.t

dl on receiving comprainu from any other user of wirelew teHPiny

PAPER

11

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EH, the Hcofwgeoded welHaetelshonT Phonetdtaphabet GOMUR would be sent as

el Golf 2 M. Uniform Romeodl Golf 2 lese.ee Uniform Romeo

60.3kHz

bl .3 kHz

cl 0 0683 11fHt

d/ 6.63 MHz

The effect..ecapacttance between tatnunalt A and B is'

a/ 1400 pF

b) NO PT

cl 285 pE

dl 560 PE


Intn Raclin

experience as you can. One without theother is likely to leave you high and dry.You might get through on theory alone ifyou are very good at memorizing things,but it will be a lot harder unless youactually have 'hands on' experience ofradio equipment - inside and outsidethe chassis.

Obviously the candidate with anelectrical or electronics background hasan immediate advantage in that he isalready schooled in an understanding ofhow electronic devices work; he will stillneed to be thoroughly familiar with theactual syllabus to pass. But how doesthe complete novice with perhaps only alittle physics, or not even that much tostart with, get the knowledge?

Probably the best way is a structuredcourse in a class with other candidates.In this way you will get the benefit notonly of the teacher's experience butthose of other hopefuls with varyingexperiences and see more than oneapproach, perhaps even with more thanone teacher.

To find a local radio course, first tryradio journals and popular radiomagazines - the RSGB's "RadioCommunication" (RadCom) forinstance. Also, check with your localpublic library or main district library,which should have lists of activity clubsand also local institutes which docourses of various kinds. Look for localradio or electronics clubs, or local RSGBgroups. Quite apart from attending clubtalks and meeting other amateurs, ifthere are enough candidates locallythen you can apply to the principle ofany local college to have a course set up,though you may have to find your ownteacher, or an instructor that the collegeis satisfied with. The college year startsin September, so you will have to findthis out well in advance, in time for theRAE, which is usually held twice a year,at various locations around the country.

If you cannot find any kind of local

51 collit

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coN

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al 15Hz 70.7 ma

01 11 Ha 35.4 mA

cl 15 He 35.4 rna

dl 3311z 70.7 ma

'co'nnce'cZnMeT1',reitrres=gro7:.:107t711::!774device in, renstance will be epproximatelY

al 5008 ohms

21 200 ohms

M 5000 ohms

d1 518 ohms

A ranamo, amplifying n an ellicAmgy .50.5

al class A

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dl class C

al 470 kHz

bl 1800 kHa

el 2270 kHe

dl 274010,

121.8."1 if: at ANDASS 87.45 .....

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4) G3YZ

QSL cards from the UK and the FaroeIslands.

course, there are correspondencecourses, and private students are alsooften successful. Try contacting otheramateurs in the area - consult theRSGB's Amateur Radio Call Book;again, a local library might help - youare likely to find one or two who wouldgladly advise you and share theirexperience.

Three years ago, the RAE switchedfrom question -and -answer to multiplechoice, but do not assume that this willmake the exam easy. You will still haveto know your practical circuit diagramsand be able to do straightforwardcalculations. It is helpful and speedsthings up if you have a calculator,although you can get by quiteadequately on normal arithmetic as longas you have a grasp of equations (whicha calculator won't help you withanyway). All the symbols used in the

0In Fig 1, a singe ..fend generator was IaI sh w mom to the hoe marked,

al unbelancol module.

01 balanced modmInor

hof fin amplifier

dl voltage controlled attenunor

101 In m 1 what is the puipme of two components marked A and El

al to reach frequency bench

bl to mach Nom transmit to mows

cl to pr.. upper and lower sdmaMs

dl to allow for repeater frequency

A 30 MHz half wain dipole has an in, impedance of about 8011 when the lengthand height H en.

L rnetrm

Z5

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1.5

s

exam are British Standard 3939, andare laid out in the RAE Manual - youare less likely to be mislead if you knowthese thoroughly.

The rules of thumb for the exam arealso simple: assuming you know yourstuff, and even if you don't, do twothings; read all the instructions on thepaper carefully, and give yourself timeto tackle all the questions. Time taken tomake sure you are doing the right thingis never wasted. If you can't do aquestion, leave it and go on to the next.You can always come back to it. With amultiple choice exam, don't leave anyquestion unanswered - who knows,but you might pick the right answer byaccident or inspired guesswork! Thiscompensates for the factor in the old-style exam, where some marks wereallocated for part -questions finished,even if the whole answer was not right.There is always a luck factor in exams -this will never make the differencebetween a good and a bad candidate,but may make the difference betweengaining and not gaining your licencefirst time around. And it costs money totake the exam, so never give up thepaper while the exam is still in progress!

The RAE is not a competitive exam -you have only to reach a certainstandard to pass, regardless of howmany other people pass or fail.

Make sure you are familiar witheverything on the syllabus. However illprepared you may feel, make sure youhave an overall acquaintance with thesubject before you try swatting up onspecial subjects - not only are youmore likely to get through the exam thatway, but it will stand you in better steadafterwards.

HE

121 In the Yam directional aerial arrangement shown below Me Mrectog is of lennth

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Courtesy of Ham Radio Today.Hobby Electronics, May 1983 45

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Popular Computing

GHFLYINGACE Mike Lord

HE's micro -master reviews the firstpersonal computer to use FORTH, a fastand efficient high-level language, as its'mother tongue'.IN INTRODUCING THE ACE, StevenVickers and Richard Altwasser havebroken away from the tradition ofoffering more hardware (RAM, sound,colour etc. for your money. Instead,they have decided to innovate in termsof software by choosing FORTH for theACE's 'natural' language rather thanthe various extended BASICs used bytheir competitors.

Because of this, any review of theACE must begin by looking at FORTHitself, and considering its advantagesand disadvantages as a programminglanguage.

FORTH

FORTH is not a new language. It wasoriginally developed over ten years ago.


Since then it has attracted a steadilygrowing band of enthusiasticsupporters, most of whom use it for'real' applications such as controllingmachinery or - recently - for writingfast action moving games.

FORTH was originally developed asan alternative to machine code for useon small microcomputers with a limitedamount of memory and where BASIC -like languages were often too slow forthe job. The result therefore liesbetween machine code and BASIC interms of both speed and ease of use.

Unlike BASIC programs, which areessentially a numbered list ofcommands, FORTH programs are builtup by defining new commands, startingwith the elementary low leveloperations, then using these in morecomplex commands, and so on until you

end up with a single command thatdefines the whole program.

In FORTH terminology, a 'command'is known as a 'word', and consists of adescriptive name followed by a defini-tion of what the word is to do. Thedefinition is usually in terms of otherFORTH words, although you can use amachine language routine where speedis really critical. As each word definitionis entered, it is added to a 'dictionary',and that word can then be used in thedefinition of new words. This probablysounds confusing to someone whohasn't encountered FORTH before, butthe basic principle is quite simple. If youwere to enter:

: HI 125 100 BEEP ;

then the colon at the start of the linetells the computer that you are defininga new word - called HI - and the semi-colon at the end signals the end of thedefinition. The definition of this word istherefore:

125 100 BEEP

BEEP is a pre -defined word, one ofabout 140 FORTH words heldpermanently in the ACE's ROM, and itmakes a sound using the AEC's internalloudspeaker. The two numbers definethe frequency and duration of the note.Having entered the new word definition,it will be placed in the ACE's dictionary,and now the ACE will understand theword HI as an instruction to produce ashort, sharp, tone. In fact, just typing inthe word HI will now produce the tone,since if you enter any line that doesn'tstart with a colon, then FORTH assumesthat you want it acted uponimmediately. This is an extremelyimportant feature that lets you test outnew words as you develop them.

We could now enter a second worddefinition:

: LO 250 100 BEEP ;to produce a lower note, and then playthe two notes one after the other byentering:

HI LOHaving added the two words to thedictionary, we can use them in a furtherdefinition:

TUNE HI HI LO LO HI;

so that the new word TUNE will play asequence of 5 notes.

In this way, a FORTH program isgradually built up by defining newwords to perform ever more complextasks, but by taking it one step at a time,you can construct your program in alogical and ordered manner.

Looping and ChoosingTo let you program for alternativecourses of action, FORTH has an IF -THEN -ELSE construct similar to thatfound in advanced versions of BASIC.BEGIN -UNTIL and BEGIN -WHILE -REPEAT allow you to repeat actionsuntil (or while) a particular condition ismet, in much the same manner as BBCBASIC's REPEAT -UNTIL. And if youwant to repeat an action a defined

47

Popular Computing

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tit ti Ilk tat ilk Ilk ilk ilk %it Its

Ace comes with a power pack, cassette leads, programming manual anddemonstration tape.number of times, FORTH provides a DO -LOOP construct which behaves likeBASIC's FOR -NEXT. There is, however,no equivalent to the BASIC GOTOcommand. This seems at first like aserious omission to anyone used toprogramming in BASIC, but once youget used to FORTH you find you canalways use IF -THEN -ELSE, BEGIN -UNTIL or BEGIN -WHILE -REPEAT toachieve the same result but in a muchmore elegant fashion.

Stack ItOne area where FORTH differs con-siderably from most other computerlanguages is in its use of a 'stack' to holdthe values being worked on. Mostlanguages use named 'variables' to holdvalues, so that the BASIC statement:

LET A 27 + 33tells the computer to add 27 to 33, thenstore the result in an area of memoryreserved for the variable named 'A'. Youcan also use named variables in FORTH,but the values actually being worked onat any time will usually be held in aspecial area of memory known as the'Stack'. This is best thought of as a pileof values; a new value can be added tothe top of the pile - making the pilehigher - or a value can be taken off thetop of the pile - making it shorter. All ofFORTH's fundamental operations, likeaddition, multiplication etc., work on thevalues present on the top of the stack.The '+' operator, for example, takes thetop two values off the stack, adds themtogether, then puts the result back ontothe top of the stack.

When the computer sees a number inthe line you have entered, it puts thatvalue onto the top of the stack. Forexample, if you look back at ourdefinition of the word HI, what it wasreally telling the computer to do was tofirst put the value 125 onto the stack,then put the value 100 on top of that,then execute the pre -defined wordBEEP, which takes the top two numbersfrom the stack to give the frequency andlength of the note to be produced.

Similarly, the line:

27 33 +will place the values 27 and 33 onto thestack, then replace them by the singlevalue 60. This way of writing may seembackwards at first (and - indeed - it is

known as 'reverse Polish') but you soonget used to it.

There are two main reasons whyFORTH was designed around the use ofa stack. The first is that it saves memoryspace because values are kept in RAMonly as long as they are needed, and -more importantly - because theprogram doesn't need to contain thenames of the variables (at least as longas the values are being kept on thestack). The second advantage is thatyour programs run more quicklybecause the computer doesn't have tosearch through a 'variables storagearea' to find the one you want.

DIY FORTHFORTH is really a 'Do It Yourself'language. Although it has about 140pre -defined words compared to the 90or so keywords in most versions ofBASIC, they nearly all correspond tovery elementary operations, and youhave to add your own definitions to doanything that is even slightly complex.

Take arrays for example. In BASIC, asimple DIM statement will set up anarray so that you can then refer to anelement of it by just using a subscriptedvariable such as A(27). But FORTH hasno equivalent to the DIM statement orthe subscripted variable; you have towrite special words that will let youhandle data in array form, or - moreprecisely - you have to define a routinethat can be used to set up arrays, andanother to let you refer to an individualelement of an array. At the end of theday you will be able to handle arrays ofdata at least as well as you could inBASIC, but you will have taken longer toget there.

Similarly, if you want to handlestrings, you must first define somestring handling words.

Fast FORTHWhere FORTH really scores is in doingfairly simple tasks very quickly. And,because it is much nearer to machinecode than BASIC, you have much morecontrol over what the computer isactually doing. Indeed, to programsuccessfully in FORTH you need to bemuch more aware of how the computerworks than you do with most otherlanguages, and pay much moreattention to the possible side effects of

what you are doing. For example, FORTHarithmetic is usually done using 1 6 -bitwords that can take integer valuesfrom -32768 to 32767. But there is nocheck to see if a result has overflowed,so that it will quite happily add 30000 to30000 and say that the result is -5536!FORTH enthusiasts will say, of course,that if you really want the + operator to.check for overflow then you can easilydefine a new version of the word thatdoes just that.

ACE FORTHThere is a standard for the FORTHlanguage, known as FORTH -79, and theversion provided on the ACE sticks veryclose to it. The main differences are theaddition of words to handle floatingpoint numbers, plotting, the soundgenerator, and I/O ports. There are alsosome differences in the way programsare entered and edited.

The HardwareThe ACE comes in a white vacuum -formed plastic box about the same widthas the Spectrum but deeper, heldtogether with plastic rivets along thesides and back. A label on the undersideof the box warns that there are no 'userserviceable' parts inside, and indeed thecase is fixed together in such a way thatyou can't take it apart without splittingthe plastic. This is a pity, because I amsure that many people who would beattracted to the ACE would beenthusiastic (and knowledgeable)enough to want to get at the hardware tomake minor 'improvements'.

On the model received for review, thequality of the case was poor. The edgeswhere it had been cut from the mouldwere rough, there were a couple ofnoticeable dimples on the top surface,and the holes in the case for the TV, Ear,Mic and Power sockets did not line upproperly. Worse, the bottom part of thecase was bowed so that it flexedwhenever you pressed on a key, and thekeytops sometimes caught underneaththe case top. Hopefully these were justteething problems with the first models.

Two PC board edge connectors areprovided at the back for add-ons. One ofthese is to take memory extensionand/or I/O ports. It is believed that theother is for a possible colour displayadd-on.

The keyboard has the same layout ason the Spectrum, even having the sameawkwardly positioned Symbol Shift key,and also lacks a proper space bar. But,because FORTH doesn't use keywordsin the same way that Spectrum BASICdoes, there is a blessed simplicity aboutthe key legends. Generally, each key isonly used to give upper or lower casecharacters - governed by using theSHIFT key, or a special symbol such as

which is obtained with the SymbolShift key. The keys are black with easilyread white markings.

As on the Spectrum, the keytops areall formed from a single rubbermoulding which collapses as you presson a key, but the ACE's keys feel much


Popular Computing III

4

The view inside the ACE; the chip count totals around 30 ICs!

firmer and need to be pressed muchmore deliberately. You can't type quicklyon the ACE - the keyboard just won'tlet you - so the auto -repeat feature isuseful.

On Screen

The TV display is crisp and stable butis in black and white only. There are 24lines of 32 characters each, and intypical fashion the bottom line isreserved for use as an input buffer.Characters are normally displayed inwhite on a black background, althoughyou can make any character appear inblack on white. Both upper and lowercase letters are available, as well as 16'chunky' graphics characters. Thecharacter codes used are basicallyASCII with a few additions such as thecopyright symbol and 'f' as well as 'S'and ' #

As is common practice for most lowcost computers, the characters areformed from an 8 x 8 array of pixels. Thedot patterns for the whole character setare held in a special area of RAM (theyare copied from ROM into the RAMwhen power is applied), which meansthat you can re -define any or all of themto make your own shapes in much thesame way as you can on the Spectrumor the BBC computer. A PLOT commanduses the chunky graphics characters togive a low resolution (64 x 46) plottingcapability similar to that on the ZX81.Because you can define your owncharacters, each as an 8 x 8 pixel array,you can theoretically draw shapes withan overall resolution of 256 x 192 pixels,but in practice you wouldn't use thisfacility for drawing shapes larger thanthe space of a few characters on thescreen. There is no equivalent to thehigh resolution plotting modes availableon the Spectrum, Dragon or BBCmachines.

The ACE has an internal loudspeaker,and a BEEP command to drive it, but youare limited to one note at a time and canonly vary the pitch and duration.

The cassette tape interface works at arespectable 1500 baud (about 6 secondsfor 1K bytes). You can save to tape eitherthe dictionary of new word definotionsthat you have entered, which iseffectively your program, or a definedarea of memory. A VERIFY commandlets you see if what is on tape is thesame as what is in memory. On themodel under test, a very high level wasneeded from the recorder when loading;reminiscent of the old ZX81, but other-wise the system worked reliably.

Internal MattersInside the case is a bit of a shock toanyone used to Sinclair's 'The fewerparts the better' philosophy; almost 30ICs have been packed in. Obviouslyin starting up a new company fromscratch Vickers and Altwasser could notafford the time or cost of developing acustom integrated circuit like the ULAused to replace handfuls of TTL chips inthe Spectrum, just as they didn't investin the tooling for an injection mouldedcase.

The central processor is, of course,the one we can't seem to get away from:the Z80A. The Operating System soft-ware, FORTH, and the standardcharacter set dot patterns have all beensqueezed into an 8K byte ROM. 3K bytesof RAM have been fitted, which mayseem a lot compared to the 1K of theZX81, but 1K is used to hold the dotpatterns when the machine is running,and almost the whole of another 1K isused for the TV display file, and yet morefor working space, stacks, and SystemVariables, so you are left with wellunder 1K bytes to hold your programand data. Some form of memory expan-

_ACE BOUNCER_This program was written as anexercise in using FORTH and to getsome idea of how fast a FORTHprogram will run. It moves a stararound the screen, bouncing it offthe four edges.

Similar programs written inBASIC will make a complete circuitof the screen in about one or twoseconds. This FORTH version runsat about the same speed, but onlybecause it has been deliberatelyslowed down by the 100 5 BEEPcommand in the word GO. Withoutthis restraint, the star moves so fastthat you can only see momentaryglimpses of it as it flashes aroundthe screen!

10 VARIABLE HPOS10 VARIABLE VPOS1 VARIABLE HVEL-1 VARIABLE VVEL NEWPOS HPOS @ DUP 0= IF 1

HVEL ! THEN DUP 31 = IF -1 HVELTHEN HVEL @ + HPOS ! VPOSDUP 0= IF 1 VVEL ! THEN DUP 22 =IF -1 VVEL ! THEN VVEL @ + VPOS !

WIPE VPOS @ HPOS @ ATSPACE: PRINTNEW VPOS @ HPOS AT42 EMIT ;: GO CLS BEGIN 100 5 BEEP WIPENEWPOS PRINTNEW 0 UNTIL ;

sion is essential for any but the simplestapplication.

The 181 page manual provided withthe ACE is excellent, both as an intro-duction to FORTH and as a guide tousing the ACE. It was written by StevenVickers, and is in the same light but veryinformative style as his previousSinclair manuals. One interestingchapter, Extending theA CE, gives muchmo-e information on how to add I/Oports or memory than is usual in acomputer manual, including the circuitfor a simple I/O port and examples ofsoftware to drive it.

In ConclusionThe ACE represents a brave attempt toget away from the cliche of colour -BASIC - games machine personalcomputers, but in the long term willprobably suffer from the lack of invest-ment in a professional looking case andthe absence of colour or true highresolution graphics. Now that FORTH isbecoming available as an optionallanguage for other computers such asthe Spectrum and ORIC, many peoplemay prefer to spend the extra to get themore powerful and flexible machines.The ACE will probably appeal most tothose who have a limited budget and areinterested in programming simplecontrol type applications. But eventhese potential buyers might prefer thecombination of a ZX81 with a cheap 16KRAM pack and FORTH on cassette,which adds up to about the same as anACE. HE

4 Hobby Electronics, May 1983 49

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These units are as used in the "Big Trak" computerized vehicle, and offer the experimenter inrobotics the opportunity to purchase the electromechanical pails required in building remote controlled vehicles. The unit comprises:

al 2 x 3V motors, linked by a magnetic clutch, thus enabling turning of the vehicle;b) A gearbox contained within the black ABS housing reducing the final drive speed to aripros 50rpin.

Data is supplied with the unit showing various options on driving the motors, as well as a directioncontroller circuit, enabling the unit to turn right, left or go straigt ahead.

2N3055 SCOOP!! AA NI -CADS 10 for £9.95Made by Texas full spec devices, alp each; 10for Ea; 25 for Oh 100 for E34; 250 for E75; 1000for QM.

COMPUTER SOFTWAREWe now sell a range of tapes and books forDRAGON 32, SPECTRUM, ZX81, BBC andVIC20. Send s.a.e. for list stating for which cornouter required, or call in our shop.

SIMON GAMESimorn is back again. Another supply of ready builtPC8's for this Hashing light,pulsattng tone cornputerised game is now with us. Suppled testedand working with speaker and instructions. E4.95.

COMPUTER BATTLESHIPSProbably one of the most popular electronicgames on the market. Unfortunately the designmakes it impractical to test the PC8 as a workingmodel, although it may well function perfectly. Instead we have tested the sound chip, and sell theboard for its component value only IPCB may bechipped or cracked), SN76477 sound IC;TMS1000 u -processor: Bart clips. R's. C's etc.See 160 x 140rairn. Only £1.50. Instruction bookand circuit 30p ex.

LIE DETECTORNot a toy, this precision instrument was originallypart of an "Open University" course, used tomeasure a change in emotional balance, 01 as a lieriMector. Full details of how to use it are given,and a circuit diagram. Supplied complete withprobes, leads and conductive telly. Needs 2 4Wbans Overall size 155x100x100mrn. Only E9.96

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Brand new nickel cadmium batteries by GE. scandard 1.2V at 450mA ,L4 Professional quality withsolder tags both ends. Special price. E1.40 ea. 10for 03.99 Box of 80 ON.Nicad Charger: Charges up to 4AA. C or D cells

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ELECTRO DIALElectrical combination lock ;for maximum securitypick proof. One million combinations! Dial is turned to the right to one number, left to a secondnumber, then right again to a third number. Onlywhen this has been completed in the correct sequence will the electrical contacts close. Thesecan be used to operate a relay or solenoid. Overalldia 65rnm x 60mm deep. Only E3.95.

FERRIC CHLORIDENew supplies lust arrived 250mg bags ofgranules, easily dissolved in 500m1 of water. OnlyE1.15. Also abrasive polishing block 95p.

STABILIZED PSU PANELAloe A versatile stabilised power supply with bothvoltage (0-30V) and current 120mA 2A1 fullyvariable. Many uses inc bench PSU, Ni cadcharger. gen, purpose testing. Panel ready builttested and calibrated E7.75. Suitable transforms,and pots E5.00. Full data supplied.

REED RELAYSManufacturers rejects OIL and other PCBmounting types. SP. DP and 4P make, breakand c.0 contacts. Not tested, so may be only parBally working or oic etc, so very low price packof 10 assorted El; 25 E2.00; 100 0.00.

TELESCOPIC AERIALSAs used in Sinclair microvision. 9 section100 610mna Only 95p.

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Stereo Cassette DeckCOmplete with pre -amplifiers £14.95 + £1.50 P&P

AY -3-8500 200p LM319 200pAY -5-3507 200p LM 324 35pAY5-4007 200p LM 339 60pCA 758 150P LM 380 85pHA 1156 150p LM 1458 50pCH8510KA 1000p LM 2901 80p

L 7103 400p LM 3401 80pCL 7106 750p LM 3900 55pCL 7109 800p MC 1310 150pCL8038BM 300p MC 1312CL 8048 1000p MC 1327CL 8049 1000p MC 1349

L 8260 MC 1350 80pCM7205IPG 900p MC 1357CM 7211 400p MC 1456 80pCM 7212 300p MC 1488 150pCM 7216E1 1800p MC 1489 200pCM 7216C 1800p MC 1495 320pCM 7216D 11300p MC 1496 80p

M 7217C 700p MM 53100N 200pM 7218 700p MM 57105 200p

CM 7235A 400p NE 536TM 5600 150p NE 540L

LF 155T NE 543K 200pLF 3551 100p NE 541LF 356H 100p NG 550 90pLF 357T 100p NE 555 16pLM 310 150P NG 556 40pLM 311 BOP NG 558 100p

NE 562NE 565

350p120p

TDA 1327TDA 2524

NE 566 160p TDA 2530 300pNE 5018 700P TDA 2540 350pNG 5553 120p TDA 2541 350pNG 5554 12Jp TDA 256073 350pT BA 810P 80p TDA 2571A 375p

TDA 1001A TDA 2581 325pTDA 1003A 220p TDA 2611A 225p

TDA 1004 300p T DA 3310TDA 1008 300p TDA 3950TDA 1050 250p Computer ICs

TDA 1071 2732 450p

TDA 1170 200p 4116 80p

TDA 1190 200p 2114 90p

Call in the shop for lists and abrowse. We feel sure you willbe pleasantly surprised at thestock we keep.

ALL PRICES INCLUDE VATPLEASE ADD 50p PEtP

WILMSLOWL The firm for Speakers

Bigger and Betterthe colourful Wilmslow Audio brochure-the definitive loudspeaker catalogue!

Everything for the speaker constructor - kits, drive units,components for HiFi and PA.50 DIY HiFi speaker designs including the exciting newdB Total Concept speaker kits, the Kef Constructor range,Wharfedale Speakercraft, etc.Flatpack cabinet kits for Kef, Wharfedale and many others.

* Lowest prices - Largest stocks ** Expert staff - Sound advice *

* Choose your DIY HiFi Speakers in the comfort of our *two listening lounges

(Customer operated demonstration facilities)* Ample parking *

Send 1.50 for catalogue(cheque, M.O. or stamps -or phone with yourcredit card number)

* Access - Visa - American Express accepted *also HiFi Markets Budget Card.

WILMSLOWL-ECOM

L The firm for Speakers0625 529599

35/39 Church Street, Wilmslow, Cheshire SK9 11AS

Lightning service on telephoned credit card orders!


Containsall you needto solder/de-solderany electronics project:LITESOLD LC18H 240v high performance iron, made to professionalstandards in our own works, fitted with 3.2mm bit. 2 alternative bits, 1.6and 2.4mm. Reel of 3 metres 18 swg flux -cored solder. Stainless steeltweezer. 3 soldering aids. Reel of 1.5 metres de -soldering braid. Packedin clear PVC presentation/storage wallet. Superb present - ideal forbeginner or expert.SK18H KIT SPECIAL PRICE £14.55 inc. VAT & P.P. (normal resalevalue £18.45 inc.) LC18H IRON only £6.00 (normally £7.39 )Spares, accessories and after -sales service available from us.16 -page colour catalogue - 60p. Send cheque/P.O. to LITESOLD orring for wBarclaycard)sales. 1111110111 LIGHT SOLDERING DEVELOPMENTS LTD.Spencer Place, 97/99 Gloucester Road, Croydon CR0 2DN, Surrey. Tel: 01-689 0574.

Send for my CATALOGUE ONLY 75p(plus 25p post/packing)

My all-inclusive prices quoted in the Catalogue arethe lowest. All below normal trade price - some at

only one tenth of manufacturers quantity trade.See my prices on the following:

CAPACITORS . . ELECTROLYTIC; CAN, WIRE END, TANTALUM, MULTIPLE,

COMPUTER GRADE, NON POLAR, PAPER BLOCK, CAN, POLY, MICA, CERAMIC.

LOW AND HIGH VOLTAGE, RESISTORS. 118th WATT TO 100 WATT; 0.1% TO

10% CARBON, METAL AND WIRE WOUND + NETWORKS. FANS, BATTERIES,

SOLENOIDS, TAPE SPOOLS, VARIABLE CAPACITORS AND RESISTORS,

TRIMMERS, PRESETS, POTS . . . SINGLE, DUAL SWITCHED, CARBON,

CERMET AND WIREWOUND, SINGLE OR MULTITURN, ROTORY AND SLIDE.

DIODES, RECTIFIERS, BRIDGES, CHARGERS, STYLI!, SOCKETS, PLUGS,

RELAYS, TRANSISTORS, IC'S, CLIPS, CRYSTALS, ZENERS, TRIACS,

THYRISTORS, BOXES, PANELS, DISPLAYS, LED'S, COUPLERS, ISOLATORS,

NEONS, OPTO'S, LEADS, CONNECTORS, VALVES, BOOKS, MAGAZINES,

TERMINALS, CHOKES, TRANSFORMERS, TIMERS, SWITCHES, COUNTERS,

LAMPS, INDICATORS, BELLS, SIRENS, HOLDERS, POWER SUPPLIES, HARD-

WARE, MODULES, FUSES, CARRIERS, CIRCUIT BREAKERS, KNOBS,

THERMISTORS, VDR'S, INSULATORS, CASSETTES, METERS, SOLDER,

HANDLES, LOCKS, INDUCTORS, WIRE, UNITS, MOTORS, COILS, CORES,

CARTRIDGES, SPEAKERS, EARPHONES, SUPPRESORS, MIKES, HEATSINKS,

TAPE, BOARDS and others.

Prices you would not believe before inflation!

BRIAN J. REEDTRADE COMPONENTS

ESTABLISHED 26 YEARS161 St. Johns Hill, Battersea, London SW11 1TQ

Open 11 am till 7 pm Tues. to Sat. Telephone: 01-223 5016

For a detailed booklet onremote control - send us 30pand S.A.E. (6" x 9") today.

r HOME LIGHTING KITSThese kits contain all necessary components and fullinstructions & are designed to replace a standard wallswitch and control up to 300w of ',Ming.TDR300K Remote Control £14.30

DimmerMK6 Transmitter for above E 4.20

TD300K Touchdimmer 7.00TDEJK Extension kit for 2 -way

switching for TD3OOK £ 2.00

f 3.50LD300K Rotary ControlledDimmer

r DVM/ULTRA SENSITIVETHERMOMETER KIT

This new design is based on theICL7126 la lower power version ofthe ICL7106 chip) and a 31/2 digitliquid crystal display. This kit willform the basis of a digital multi -meter (only a few additional re-sistors and switches are required -details supplied),or a sensitive digital thermometer )-50°C to+ 1501C)reading to 0.1°C. The basic kit has a sensitivity of200mV for a full scale reading, automatic polarity in-dication and an ultra low power requirement -givinga 2 year typical battery life from a standard 9V PP3when used 8 hours a day, 7 days a week

Price £15.50

1

CIREI

4

rer.23 -NOTE DOOR CHIME crO

Based on the SABO600 IC the kit is supplied with allcomponents, including loudspeaker, printed circuitboard, a pm -drilled box 195 71 x 35mm) and fullinstructions. Requires only a PP3 9V battery and push -switch to complete. AN IDEAL PROJECT FOR

,BEGINNERS. Order as XK102 £5 00J

XK113 MW RADIO KITBased on ZN414 IC, kit includes PCB, wound aerial andcrystal earpiece and all components to make a sensitiveminiature radio. Size: 5.5 x 2.7 x 2cms. Requires PP39V battery. IDEAL FOR BEGINNERS. £5.00

COMPONENT PACKSPACK 1 650 Resistors 47 ohm to 10 Mohm - 10 per

value £4.00PACK 2 40 x 16V Electrolytic Capacitors 101.4F to

1000uF -5 per value £3.25PACK 3 60 Polyester Capacitors 0.01 to 1uF/250V -

5 per value £5.55PACK 4 45 Sub -miniature Presets 100 ohm to 1 Mohm

- 5 per value £2.90PACK 5 30 Low Profile IC Sockets 8, 14 and 16 - pin

- 10 of each £2.40PACK 6 25 Red LEDs 15mm dia, I £1.25

MINI KITSMK1 TEMPERATURECONTROLLER/THERMOSTATUses LM3911 IC to sense tempera-ture (80°C max.) and triac to switchheater. 1KW £4.00MK2 Solid State ReleyIdeal for switching motors, lights,heaters, etc. from logic. Opto-isolated with zero voltage switching.Supplied without triac £2.60MK3 BAR/DOT DISPLAYDisplays an analogue voltage on alinear 10 element LED display as abar or single dot. Ideal for thermo-meters, level indicators, etc. May bestacked to obtain 20 to 100 elementdisplays. Requires 5-20V supply.MK4 PROPORTIONAL £4.50TEMPERATURE CONTROLLERBased on the SL441 zero voltageswitch, this kit may be wired to forma "burst fire" power controller,enabling the temperature of an en-closure to be maintained to within0.5T. Max. load 3KW E5.55MK5 MAINS TIMERBased on the ZN1034E Timer IC thiskit will switch a mains load on for off)for a preset time from 20 mins. to 35hrs. Longer or shorter periods maybe realised by minor component

,changes. Max. load 1KW. E4.50

Have you got our FREE ORANGE CATALOGUE yet?NO?! Send S.A.E. 6" x 9" TODAY!!

It's packed with details of all our KITS plus large range of SEMICONDUCTORS.including CMOS, LS TTL, linear, microprocessors and memories, full

range of LEDs, capacitors, resistors, hardware, relays, switches etc.We also stock VERO and Antex products as well

as books from Texas Instruments, Babani and Elektor.ALL AT VERY COMPETITIVE PRICES.

ORDERING IS EVEN EASIER - JUST RING THE NUMBERYOU CAN'T FORGET FOR PRICES YOU CAN'T RESIST.

Answeringand give us your Access or Barclaycard No service evngsor write enclosing cheque or postal order.Official orders accepted from schools, etc. & weekends

5-6-7 8-9-10

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TE11LECTRosONn

ICSoa

London W7 3SJ

No circuit is complete without a call to

lAdd 55p postage & packing +15% VAT to totalOverseas Customers;

Add E2.50 (Europe), E6.00 (elsewhere) for p&pSend S.A.E. for further STOCK DETAILS.Goods by return subject to availability.

OPEN 9am to 5pm (Mon to Fril10am to 4pm (Sat)

ALLPRICES

EXCLUDE VATTEL: 01-567 8910 ORDERS

01-579 9794 ENQUIRIES01-579 2842 TECHNICAL AFTER 3PM

LCD 31 DIGIT MULTIMETER16 ranges including DC voltage (200 my -1000v) and AC voltage, DC current 1200 mA-10 Aland resistance 10-2 MI + NPN & PNP transistorgain and diode check. Input impedance 10M.Size 155x88x31 mm. Requires PP3 9v battery.Test leads included ONLY £29.00

L.

ELECTRONIC LOCK KIT XK101This KIT contains a purpose designedlock IC, 10 -way keyboard, PCBs and allcomponents to construct a DigitalLock, requiring a 4 -key sequence toopen and providing over 5000 differentcombinations. The open sequence maybe easily changed by means of a pre -wired plug. Size: 7 x 6 x 3 cms. Supply:5V to 15V d.c. at 40uA. Output:750mA max. Hundreds of uses fordoors and garages, car anti -theftdevice, electronic equipment, etc. Willdrive most relays direct. Full instruc-tions supplied.

ONLY £10.50Electric lock mechanisms for use withlatch locks and above kit £13.50

DISCO LIGHTING KITSDL 1000KThis value -for -money kitfeatures a bi-directionalsequence, speed of sequenceand frequency of directionchange, being variable bymeans of potentiometers andincorporates a master dimming control.

012100K£14.60

A lower cost version of the above. featuringundirectiona I channel sequence with speedvariable by means of a pm -set pot. Outputsswitched only at mains zero crossing pointsto reduce radio interference to a minimum.

Optional opto input DLA1Only £8.00

Allowing audio ("beat"/ 60p-light response.

DL3000KThis 3 channel sound to light kit features zerovoltage switching, automatic level control &built in mic. No connections to speaker or amprequired. No knobs to adjust - simply connectto mains supply & lamps.(1 Kw/Channel) Only £11.95

A


Feature

THERE IS NOT much doubt that English -made loudspeakers are the finest in theworld - without any disrespect to ourAmerican cousins or the latter-daySamurai. When it comes to "Zen andthe Art of Loudspeaker Construction",the British speak little but work marvels.But not on the cheap. A really first classpair of 'speakers almost requires a

mortgage, and even a decent pair won'tleave much change from a month's pay.You will therefore understand myinterest when I was offered the chanceto review a pair of self -assembly'speakers from Wilmslow Audio!

The range offered by Wilmslow is verylarge. Almost every major Britishmanufacturer is represented, includingtop names such as Kef, Celestion,Chartwell, and Jordan Watts. In theHigh Street, prices for such 'speakersrange from the barely affordable to "Ohmy god", so the great attraction of self -assembly 'speakers has to be theopportunity to acquire a good set at anequally good price.

Hifi HypeIt's always easy to buy an argument,amongst hifi buffs, as to whichcomponents of a hifi system are themost critical; it depends really on whoyou talk to and on the degree of difficultyinvolved in engineering particularelements.

Amplifiers, for example, are no longermuch of a challenge in the normal lineof hifi equipment, so that anymanufacturer worthy of the name oughtto be able to produce an amp that iscapable of around 50 watts per channelwith 0.1% distortion and a frequency

At this stage the cabinet has beenassembled (note the lines ofbathroom sealant around the insideof the joints). The crossover boardhas been screwed to the rear paneland the leads taped out of the way.

response ruler flat from 20Hz to 20kHz.Of course, there are 'exotics' that offerclass and facilities way above the norm,but in average hifi terms buying an ampcomes down to ''pounds perwatt" - unless you are undulyimpressed by an excessive number ofknobs, indicators etc. and a front panelas glossy as the advertising brochure!

Similar arguments apply to hifituners, and as for cassette decks - ifyour budget stretches to a Nakamichithen well and good. Otherwise you'llhave to be satisfied with less than best.

The argument starts to warm upwhen discussion turns to loudspeakers,turntables, tone -arms and cartridges. Inrecent years, computer -aided designand analysis has taken much of the'magic' out of the engineering of thesecomponents; actually, it always was(is?) a case of juggling thousands ofvariables, partly by mathematics andpartly by inspired guess -work.Computer techniques, with thecapability for handling all thesevariables easily, have simply removedmost of the guess -work!

However, appreciation of the virtuesof different 'speaker or turntabledesigns remains mostly subjective;

The two sections of acousticwadding are rolled up and placedinside the cabinet, then teased outto fill the entire space.

Olt;Barry Foster

With self -assembly lourfor your money witl

what you like depends on what youhear. On the other hand, what you liketo hear will decide where you will spendmost of your hifi budget.

Briefly, the quality of the turntable,arm etc. will determine the bottom limitof distortion and the upper limit offrequency response (assuming that theamplifier is up to the mark). The'speakers may also contribute todistortion but, more importantly, set thebottom limit of the frequency response.

So if, like me, you are a person whoputs more store by meaty, beefy bassthan in crisp clean highs at the upperlimit of hearing, the loudspeakerbecomes the most important element inthe hifi system. Thus a self -assembly kitprovides the means to spread yourbudget to the best advantage, while atthe same time allowing you to acquire afirst class set of 'speakers at a moderate


Feature

eakers you get moret sacrificing quality.

price and leaving cash in hand to outlayon other items.

Questions and AnswersPrice is not all, however, if performancedoes not follow, so the question must beasked: how good are self assembly'speakers?

The answer, reassuringly, is - verygood indeed! The kit chosen for reviewwas the modestly priced dB12W kit,designed for amplifiers between 15 and75 watts, and provided the assemblyinstructions are followed withreasonable care, they will produceresults as good as any store-boughtitems of comparable size and design.

In a NutshellThe dB12W kit is second from the top inWilmslow's dB kit range. It is designed

for amplifiers in the range 15-75 wattsand is given a five star assembly rating,meaning that no woodworking orelectronic skills are required. Thedimensions of each cabinet are 540 x255 x 230mm, and they are designed forstand mounting some 300mm off thefloor and, ideally, at least two feet awayfrom walls. The units are described asmedium sensitivity infinite baffle'speakers, and contain three drivers anda pre -assembled three-way crossoverboard (which is the only component notmanufactured in the UK).

The lower driver is a speciallydesigned 61/2in 'lower bass' unit, which,together with the 61/2in mid/upper-bassdriver, gives a surprisingly goodresponse for a unit of its size; thetransient response is sharp, without anytrace of sogginess. The treble driver is a1in soft -domed tweeter, dilled withferrofluid, which produces accuratehighs all the way to the top.

They are perhaps a little too strong onmid -range 'presence' for my taste, but alittle bass and treble equalisation easilycompensates. When boosted slightly,the bass is always clear and distinct,even though the speakers are floor -mounted rather than set up on stands as

The central 'shelf' (visible throughthe tweeter opening) is installednext, then the front baffle -board isglued into place. The wires are ledout through the openings, ready toconnect up to the driver units.

recommended. Likewise, the highs arecrisp and clean and the stereo image,though the room does not permit idealplacement, is well separated.

The next question, of particularinterest to hifi nuts who may not also beDIY buffs is: how easy are they toassemble? The answer is once moreagreeable; putting together the dB12W'speakers occupied a leisurely Saturdayafternoon, with plenty of time to watch"World of Sport" while the glue dried!

The cabinets are constructed from amaterial described as 'VIDE, whichlooks like very high density chipboard tome; in any event, it certainly lives up tothe makers claim that "It machinescleanly and accurately without theragged edges associated with chipboardcomponents". The side and top panelsare prefinished solid African Walnutwhich, together with the simple butreliable construction method describedlater, give the finished units a solidappearance, not at all like a 'homemade'unit.

Doing It YourselfThe speakers arrived, in bits, in twoweighty cardboard boxes, and whenunpacked formed an impressive ifconfusing array of high -densitychipboard panels, foam -shrouded driverunits, printed circuit boards, blackacoustic foam, white wadding, andglossy brown African walnut panels.The instructions were roughly copiedand seemed not altogether comprehen-sive, though in the end they provedadequate (remember the GoldenRule - when in doubt read theinstructions!).

Nearly complete, the driver unitshave been screwed into place. Thebass and mid -upper units arephysically very similar, and must bechecked carefully to make sure theygo in the right openings (bass at thebottom).


FeatureTools required to assemble the kit are

minimal: a pair of cross -headscrewdrivers, a tube of woodworkingglue, a roll of masking tape, a damp clothto remove excess glue, a small power orhand drill with a 1/Bin bit and a smallhammer.

My initial doubts about theinstructions were soon resolved. Thesesaid, in effect, "apply glue to therelevant surfaces, slap the panelstogether and hold them in place withmasking tape while they dry". What? Noscrews, clamps or wood presses? No,not one; the panels are so finely andaccurately machined that the box canbe assembled virtually free-standing,the precision joints providing sufficientrigidity to hold the whole thing in place.The masking tape gives a slightly tighterand more securely sealed joint, butmostly seems to be for insurance (andassurance for the doubting constructor).

The remainder of the construction isequally simple, as illustrated by theaccompanying photographs; there areone or two points worth noting, though.

One of the secrets of obtaining goodclean bass response is to ensure thatthe cabinets are completely airtight; theslightest leak and your prized 'speakerswill wheeze like a bagpipe with a hole init -and sound almost as appealing! Thetrick I used was to seal the inside of eachjoint with a liberal bead of ordinarybathroom waterproof sealant, of thetype sold in most DIY shops. Thisensures that the panels are completelyairtight (watertight, too). The front

baffle -board cannot be sealed this way,however, so I applied a thin line of glueto the outside of the joint, carefullywiping off the excess with the dampcloth. These steps are perhaps notnecessary if you take due care to securethe joints, but the cost and effort isminimal for a guaranteed result!

The pre -assembled crossover boardcan be mounted anywhere within thecabinet, as long as the leads will reachfrom the PCB to the drivers. I found itodd that these mounting holes were notpre -drilled, as this would have simplifiedthe construction considerably, butapparently Wilmslow have found thatpeople have different ideas aboutlocating the crossover board within thecabinet. Personally, I don't see that itmatters.

I had some slight difficulty with theconstruction at two stages only: thefoam gasket in which the mid -range andbass drivers sit has to be cut up and re-arranged around the flange to clear thebolt holes; then I found that the tweeterdid not want to sit firmly in its milledrebate, apparently because the centrallymounted shelf was blocking it.Fortunately, the glue had not yet driedso I was able to move the shelfbackwards, secure the tweeter, thengently knock the shelf forward intoposition.

The only items with which I was justslightly unhappy were the bananasockets supplied for connecting up the'speakers to the amplifier. While theyhave proved adequate, so far, I would

have preferred solid spring -clip connec-tors for that extra measure of security.

Finally, though, when the dB12W kitwas completed and booming out "TheWall" at top volume (the neighbours hadbeen warned!), minor problems andquibbles were blasted into insignifi-cance.

There is one other cautionary notewhich, however, applies to most makesof 'speakers, rather than the dB12W kitin particular. Like most modernloudspeakers, the dB12Ws are frontedby an acoustically transparent foamgrille, which nicely complements thepolished woodwork and looks at homein most decorative schemes. But thefamily cat seems to find the foam totallyirresistable, preferring it to all otherscratching posts!

The dB12W kit is priced at £108including VAT, with postage andinsurance £4.50 extra. Other self -assembly kits in the range go from thedB4C, at £35.95, up to the JordanSystem 4, which is priced at £330 andrequires considerable woodworkingskills (or, as Wilmslow put it, "Built anygood sideboards lately?"). There aremany types in between and it is worthchecking the Wilmslow cataloguebefore coming to a decision.

Write to Wilmslow Audio Ltd,35/39 Church Street, Wilmslow,Cheshire SK 9 1 AS, or telephoneWilms/ow (0625) 529599.

HE

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2838222838232N38242838662839032839042839052839062841232841252N43912N43922844002844012844022N44032844102N44162 N48562N48572 N49182 N4919284920284921

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LIQUID CRYSTALDISPLAY MODULESPCIM177 Frequency Counter5 Digits, 0.35"FM, SW, MW, MHz. KHzAnnunciatorsSample and Hold CapabilityReset Capability25 Selectable IF OffsetsPrescaler AvailableIncanciescent BacklightingSupply Voltage 5vOperating Current arriA

95p95p75p75p75p90p90p90p40p413p

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£17.15PCIM176 Digital Meter Module3; Digits, 0.5'

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£22.50Modules are supplied with DataSheet.

FIBRE OPTICPOLYMER CABLE

A 10m coil of lmm core opticalfibre cable sheathed in blackpolyethylene for protection

ALFAC ETCHRESIST TRANSFERS

Make your own Printed CircuitBoards with our PCB transfers Draw your artwork on 0.1" grid Transfer to copper boardusing carbon paper Burnish the Allay transfers tothe board using a spatula usingcarbon marks to assist in accuratealignment Using Agee chemical eraser tocorrect mistakes Etch in Ferric ChlorideEC900 /1 0.1" Edge ConnectorEC902 /1 0.156' Edge ConnectorEC940 0.016" LinesEC941 0.031" LinesEC942 0.039" LinesEC943 0.049" LinesEC944 0.061" LinesEC945 0.079" LinesEC946 0.100' LinesEC947 0.124" LinesEC950 /1 0.031" 90. BendsEC950 /2 0.061" 90. BendsEC952/1 0.031" 30°,45°,60.BendsEC952/2 0.061" 30°,45°,60.BendsEC908 0.063" PadsEC910 0.094" PadsEC911 0.189" PadsEC960/1 TO -5 Transistor PadsEC993 /1 IC PadsEC997/1 IC Pads with tracks

between pads5 identical sheets in sealedpack 195pIndividual sheets 45pSpatula AR4 for burnishing 45pAlfac knife 180pSpare Blades (pack of 101 280pAlfac Eraser 40pAlfac Precision GridsPolyester film, matt finish0.14mm thickness, 20 lines/inA3 199pA4 100pDouble Sided Fibreglass Board1/16" thickness, 1oz Copper5" x 4" 2595' v 8" 45p

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CRYSTALS32.768KHz 100p 6 000MHz 180p

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2.4576MHz 225p 10.000MHr 170p3.0000MHz 240p 16.000MHz 190p3.5795MHz 120p 18.432MHz 150p3.6864MHz 240p 19.6608M4z 240p4.000MHz 150p 20.000MHz 200p4.193MHz 190p 27.000MHz 170p5.0688MHz 240p 48.000MHz 1709

INFRAREDTIL32 Emitter 54pTIL38 Emitter 45pTIL78 Phototransistor 54pTIL100 Photodiode 70p

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COMITECH ELECTRONICS, TRANSISTORS

C1078BC108CBC109CBC113 4BC115,6

C119 AC139 *C140

BC141C142%3

BC180 *BC161C169C

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CI 73C801776BC178CBC179C *FIE18288C18313/ CBC1848 /C13C21291BC213/3/CBC214B/CBC23713BC2388/CBC239B/CBC251BC25711BC259BC301 /260303/4BC3074/ 8BC3088/CBC309B/C8C327BC328BC337 *BC338B C384BC413CBC414CBC415CBC416C

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ComtechElectronics

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IIMBERMIIIIAAI19 9p0447 9P0490 7p0491 7p0495 8p04200 7p04202 SP84013 6084%16 7p1544 7p114914 * 3p114916 4p1144148 * Op1144001 3p1N4002 4p1N4003 4p1144004'5 5p1N4006/7 6p1145401 11p1N5402 12p1N5403 13p1N5404/5 14p1 N5406/7 15p

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CO WON( NT PACKS SUPER LOW PRICESCPI 30 IC sockets 8, 14, 16 pin 110 of each)CP2 20 BC182, BC212 Transistors 110 of each/CP3 20 BC549/BC559 Transistors 110 of each)CP4 6 2142222 NPN TransistorsCP5 6 2142906 PNP TransistorsCP6 6 2N29054 TransistorsCP7 100 1N914 DiodesCP8 100 1N916 DiodesCP10 100 I N4148CP11 10 MC14581Dual Op. Amp.1CP12 20 BAX13 DiodesCP14 50 400mW Zeners, 2 each of 2V7 -33VCP15 50 1.3W Zeners. 2 each of 4V7 51VCP16 50 Mixed Electrolytic capacitors110, 16. 25 and 50V Radial, loP to 1000uF/CP17 4 LF351 JFET Op. Amps, E1,70°CP18 4 LF353 JFET Op. Amps E3.00/CP19 50 Mixed LEDs ECM`CP20 100 l W, 1% Metal Film resistors E2.50*

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SAFGAN OSCILLOSCOPES- 5 mV/div sensitivity. Choice of Band-width 10, MHz. 15 MHz, 20 MHz. 1S/div-100n S/div. Calibratedtimebase. Solid trigger with bright line auto, normal and TV.XY facility. Z modulation. Calibration output. Bright and cleardisplay. Portability. 'Model DT410-10 MHz f205.85.Model DT415-15 MHz £217.35. Model DT420 20 MHz£228.85. Send S.A.E. FOR FULL spec.

THANDAR TM354 3', DIGIT LCD DIGITAL POCKET MULTIMETERDC volts 1 mV to 1000V AC volts 11/ to 500 V AC rms DC current1/ua to 2A Resistance 1.(tto 2 M(2 Diode checks Basic accuracy t.(0.75% of reading + 1 digit) Battery life typically 2000 hrs leadsinc. £45.94 40KV Probe £34.95Universal test lead set £12.95.

KD55C LCD DIGITAL MULTIMETER 31 digit Auto zero Auto polarity Full overload protec-tion 10 Meg0 input impedance Over range and low battery in-dication DC volts 200 mV -1000 V 5 ranges AC volts200 mV -700 V 5 ranges DC current 200 p.a 10 A 6 ranges ACcurrent 200 iia-10 A 6 ranges Resistance 200 0-200 Megf/ Complete with battery, test leads, spare fuse and carrying case£39.95

fliANDAR SC110 SINGLE TRACE LOW POWDER 2"OSCILLOSCOPE Bandwidth DC to 10 Mhz Sensitivity: 10mV/div to 50 V/div. Sweep speeds: 0.1/u secs / div to 0.5 secs/div.

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Feature

THE ELECTRONIC REVOLUTION:THE ELECTRONIC AGE

For better or for worse, the Atomic Age began on 16th July,1945. The Electronic Age dawned just two years later with less

of a bang, though with equally significant after-effects.John Biggins

IT IS VERY RARELY indeed that the birthof a new era can be located exactly on aparticular day. The explosion of the firstatomic bomb on 16th July 1945 atAlmagordo, New Mexico is the twentiethcentury's most obvious candidate for thetitle of a day which changed the world forever. But there have been a few others,and the events of 23rd December 1 947at the Bell Laboratories certainly give thatdate a strong claim to be one of history'sgreat turning points. On that day theworld's first transistor was made to work.

Some inventions creep up upon theworld rather than burst upon it. Faraday'smagnetic induction demonstration inAugust 1831 took a good half -century toturn into even the beginnings of an elec-tric power industry while wirelessdawned so gradually that we cannot evensay with any certainty who transmittedthe first signal. Some inventions like tele-vision were eagerly awaited for decadesbefore anyone could produce a workablesystem, while other like radio -telephonylay around for years before anybodyrealised what could be done with them.

But the transistor fell into none ofthese categories. Its birth that dayrepresented the pinnacle of nearly thirtyyears' concentrated research by some ofthe most talented physicists in the world,all labouring with the conscious aim ofconstructing a solid-state analogue of the

wireless valve. And over the previousthree years, Bell Labs alone had investedseveral million dollars and some of its bestresearchers in the project. Nor were theimplications of the event lost on thosepresent. No one had much idea of the sortof world that the transistor would haveproduced thirty-five years later but allthose who were there seem to have beenconscious that something out of the or-dinary had happened and that thingswould never be the same again. In theevent it took a decade for the transistor tobe perfected and built into electronictechnology, but when this happened itpushed the science of electronics into anage of exponential growth which hasdone more to change the world in the lastgeneration than steam did in the two cen-turies before that.

Like its near -contemporary the atombomb, the transistor is a classic case ofdevelopment not by technological push,but by demand-pull. The state wanted thebomb and the corporations wanted thetransistor for their own purposes, andboth were prepared, whether the projectturned out to be feasible or not, to investany amount of money and time andresearch talent towards achieving it.

The idea of a solid-state transducerwas almost as old as wireless itself. Infact, wireless wave detection began witha primitive semi -conductor, the coherer,

and continued for many years afterwardswith another form of the semi -conductorin the shape of the crystal detector. Look-ing back, you might almost see the half -century of thermionic valve developmentfollowing Fleming's diode of 1904 as ablind alley in electronics history. Valvescame in largely to make up for the defici-ences of the crystal detector: its fragility,its need for constant delicate adjustmentand above all its puny current output.Valve manufacture began by having ac-cess to all the resources and experience ofthe light -bulb industry out of which it hadaccidentally sprung, and the valve's ver-satility as oscillator, detector or amplifierled to its dominating radio fromabout 1919 onwards.

Closing the ValveValve design became remarkably

sophisticated between the Wars in thehands of specialists like Philips of Eind-hoven and the Second World War pro-duced great advances in miniaturisation.But even in the 1 930s it was beginning tobe apparent that the law of diminishingreturns applied to valve development asto everything else. Research and develop-ment could reduce some of the valve'smany drawbacks, but could never abolishthem: its size, its fragility, the expense ofits manufacture, its large power require-ment, its need for cooling (40 gallons ofwater per minute for some of the gianttransmitter valves of the mid -1 920s) andits highly unpredictable life -span. Forthese reasons interest in semi -conductorsnever died away, despite the apparentdeath of the crystal receiver some timeafter 1930. For one thing, pure un-directed speculative research went itsown sweet way during the 1920s and1 930s. Physicists like Pohl at GottingenUniversity carried on a long pre -1914tradition of research into the electricalproperties of crystals, though this wassometimes more by accident than bydesign: as in Pohl's case, where Ger-many's ruined economy in the years after1918 prevented him from getting hold ofliquid oxygen to study gas conductivityand obliged him to look at solids instead.

Most of this research was quite inno-cent of any immediate practical applica-tion but, at the back of it, the idea of asolid-state analogue to the valve wasnever far away. One Lilienfeld patented acrystal amplifier in Germany in 1925,though none was ever built and argumentgoes on to this day as to whether the thingwould ever have worked if it had been. Allexperimenters had to grapple with terri-


Featurefying problems in getting crystals pureenough to experiment with, but graduallysome substances began to emerge asfront-runners. Copper oxide was in com-mon use as a rectifier during the early1930s, and in 1935 Oskar Heil attemp-ted to build a field-effect amplifier bypassing a current through a slab of thestuff forming one side of a capacitator: anidea which was to be taken up again byBell after 1945, but which was even-tually beaten by electron retention at theslab's surface. Embedding an electrode ina crystal to modulate the current passingthrough it was the obvious next step, andin 1938 Pohl and Hilsch in Germany an-nounced that they were confident of soonbeing able to use this technique with apotassium bromide crystal to produce thelong -sought successor to the triodevalve.

Enter Germanium . . .

The war which broke out the followingyear brought most German research to ahalt. But in the end it was the war'sdemands which forced development ofthe transistor ahead once more, and inparticular the development by the Allies,circa 1942, of centimetric radar. Or-dinary wireless valves had too high acapacitance to detect the returningsignal, so the crystal detector wasbrought out of retirement: this time in theform of a silicon crystal touched by atungsten cat's whisker. It worked, butnot very well. So germanium was in-vestigated as a substitute. TheMassachusetts Institute of Technologyand about forty other US research institu-tions got to work on the problem, and bylate 1943 germanium detectors wereavailable which could handle up to 150volts.

When the war ended the researchteam at Bell Labs, Brattain, Barden andShockley, were tinkering once more withthe field-effect transistor, though thistime as part of a vast programme aimed atproducing reliable solid-state equivalentsof the valve. The field-effect approachwas eventually defeated by the surfaceretention which had beaten Heil a decadeearlier. But point -contacts with agermanium crystal turned out to be farmore promising. It was a semi -conductorof this type, soon to be christened thetransistor, which was successfully testedat Bell Labs two days before Christmas1947. The more familiar junction trans-istor followed soon afterwards and thefirst public demonstration was given atthe end of June 1948.

Contrary to later legend, Bell was anx-ious from the very first to get the trans-istor as widely used as possible as soon aspossible. To this end it was prepared togrant manufacturing rights at veryfavourable terms. For the first few years,though, there were few takers. Up untilthe spring of 1953 in fact the main optantwas the hearing -aid manufacturerRaytheon which was not too concernedabout sound quality so long as it could getminiature, low -power amplifiers. Wire-less, television, the telephone manu-facturers and (strangely enough) themilitary showed very little interest at first.True, apart from its size and its low power

requirement the transistor offered fewimmediate advantages over valves. Thefirst generation were noisy, expensive(about eight times the price of anequivalent valve in 1950), limited in thevoltages they could tolerate and limited intheir frequency response. Manufacturingmethods were often astonishinglyhaphazard by the standards of a genera-tion later, not so much designing a batchof transistors to fit a desired range ofcharacteristics but rather making thebatch and then sifting out those trans-istors which measured up to the require-ments. And there was always the prob-lem of minute traces of impurity left in thecrystals, known collectively as 'sudden-deathnium', and the reason for the failureof many early semi -conductors. Butabove all these difficulties there was theattitude of the industry itself. Though in-terested in solid-state devices, theengineers of the great American and Euro-pean electronics firms were men who hadgrown up with valves from their earliestyouth. For this reason they tended toregard the transistor as a mere valve -substitute until well into the 1950s, bywhich time it was establishing itself as atechnology in its own right and develop-ing the sub -technology of small-scale in-tegrated circuitry which was to lead to themicro -chip in the early 1 970s. This con-servatism may have had a great deal to dowith the electronics industry's greatmigration to the Far East from the late1950s onwards.

The thing that really made the trans-istor's fortunes, though, was the provi-dential development, at about the sametime, of the digital computer. But unlikethe transistor the computer was not pro-pelled into an eagerly waiting world by amassive research programme. Instead itcrept up on the human race almostunawares.

Babbage's "Analytical Engine" wasperhaps the earliest computer - amachine designed specifically forperforming mathematical calculations.(British Crown Copyright, Science Museum, London.)

The idea of calculating by machinewas scarcely a new one in the late 1 940swhen the electronic computer began todawn upon the public consciousness. Theabacus, Napier's bones, the slide rule(remember the slide rule?), Pascal's cal-culator and the Burroughs comptometerwere all attempts - more or less unsatis-factory - to rid calculation of some ofthat mind -numbing drudgery involved in

projects like the one, about 1840, whichhad an entire company of Prussian armyengineers scribbling away for six monthsto calculate the curvature of a single lens.In 1 833 the mathematician Charles Bab-bage had designed (but not built) hisAnalytical Engine: the world's first projectfor an analogue computer with input, out-put and some sort of memory. At the veryend of the nineteenth century the increas-ing demands of each successive US cen-sus had produced a number of increas-ingly elaborate card -processing machinesto deal with the returns. But true com-puters required an accuracy far beyondthe reach of even early twentieth centuryprecision engineering, and in themid -1 930s the valve began to be built in-to electronic analogue calculatingmachines at Harvard University and BellLabs.

As with the transistor, the demands ofthe Second World War pushed develop-ment forward and began the transitionfrom calculator to true computer. Notonly the Manhattan atomic bomb projectbut also ballistics trials required calcu-lations of an unheard-of complexity, farbeyond the capacity of human beingsworking unaided. And in this area the Har-vard Mark 1 electronic calculator wasable to score a notable triumph in 1942when it predicted - correctly, as it turnedout - that the German army would neverget anywhere with the electricallypowered long-range gun which it was try-ing to build. Meanwhile, across the Atlan-tic, the Enigma code -breaking operationrequired the building of a succession of in-creasingly powerful electronic cipher -machines at Bletchley Park. On a moremundane level, the vast complexity ofmodern armed forces led to the develop-ment of electronic personnel selectors inan effort to sort out the right man for thejob from among the millions available.Evelyn Waugh's novel Sword of Honourmentions one of these latter contraptionsinstalled in a War Department office inLondon circa 1943. And beyond thestrictly technical considerations of elec-tronic systems design, the war led to thefirst concentrated, systematic study ofoperational logic, information flow anddecision -making: all areas essential to thecreation of artificial intelligences after thewar was over.

. . . And the ComputerThe value of electronic calculation was

so evident by the time the war ended thatthe US Government was keen to sponsorthe building of the first true electronicanalogue computer ENIAC at the Univer-sity of Pennsylvania in 1946. Theprevious year John von Neumann hadsuggested the use of the binary systemfor electronic calculation, and after Cam-bridge University's EDSAC in 1947 allcomputers went over to digital operation.Meanwhile Pennsylvania University wasbuilding ENIAC's successor EDVAC withthe first magnetic core memory, and com-puters were moving outside the field ofstrictly scientific calculation with the USAir Force's Whirlwind flight -simulator.Likewise the universities and governmentdepartments lost their monopoly of com-puter ownership in 1952 when GEC ac -


Feature

friorritt, Fr

frarrifili ;sto error errs.

More than a hundred years after Babbage, the ESDAC I computer was built inCambridge. It was no smaller, but a lot faster!

quired its Univac I, the first computer inthe world to be owned by a private firm.

The trouble with these early com-puters was their sheer size and unre-liability. Bell's Model V in 1944 containedover 9,000 valve relays and fifty piecesof teletype equipment. It weighed tentons and took up over a thousand squarefeet of floor -space. Heat dispersal fromthese forests of valves was a major pro-blem and power requirements were vast.ENIAC used 1 30kW and is said to havedimmed lights over half of Philadelphiawhen it was switched on. Above all,down -time was huge, given the numberof valves, their unreliability and the dif-ficulty of getting at them to replace them.When it arrived on the scene at the end ofthe 1 940s the transistor was the answerto the computer builder's prayers, with itsminiscule size, cool operation, low powerrequirement and - post 1953 or there-abouts - long life. From about 1955 on-wards the valve began to be ousted by thetransistor in computer construction, andas the transistor took over the computerbegan to move out into the world.

At the end of the 1 940s the expertshad confidently predicted that a countrylike Britain would never need more thantwo or three computers to serve all itsneeds while the USA itself would only re-

quire a hundred at most. But as is the waywith these things, the increase in supplycreated its own demand. As the computerbecame smaller and cheaper it was foundthat more and more previously manual ad-ministration jobs could be handed over tothe machine: not just censuses and scien-tific calculation, but banking and payrollsand stock control and police records.From then on it began to affect the lives ofevery one of us. Computer and transistorwere the twin foundations of the post -1 945 electronic age, and neither couldreally have existed without the other.

The miniaturization of electronicsmade possible by the semi -conductors,and the durability and low power con-sumption which they brought with them,caused another great leap forward (or up-ward) in the second half of the 1950s.After all, where would space explorationbe if it relied upon valves? The nasty blowdealt to American prestige by the laun-ching of the Sputnik in October 1957 leddirectly to the race to the Moon. But so faras this century is concerned its most im-portant consequence may turn out tohave been the birth of space communi-cations. As early as 1928 the Germanrocket pioneer Hans Oberth had sug-gested space relay stations in geosyn-chronous orbit 22,300 miles above the

The ACE computer, built in 1950, still used valves, though less of them than itspredecessor ESDAC.

(Lent to the Science Museum by National Physical Laboratories)

Earth, though in this case he proposedbeaming messages up and down byheliograph because of the limited poweravailable from the transmitters of the day.And this idea was taken up again by Ar-thur C. Clarke in 1 945. But it was not un-til the late 1950s that the idea came any-where near realisation when the UnitedStates launched its first Echo communi-cations relay satellites.

These were passive reflectors: mereballoons of metallised PVC which weresupposed to act as mirrors for microwavesignals. They were not particularly suc-cessful and it was not until July 1962that the first active relay satellite, TelstarI, was put into orbit, powered by solarcells and capable of redirecting TV signalsfor that part of the day when it was abovethe horizon. Geosynchronous orbitfollowed with the Syncom series ofsatellites launched from February 1 963onwards. By 1980, upwards of fiftycommunications satellites were in orbitwith a further fifty planned. The tariffsdemanded by the international Intelsatcorporation were too high at first for morethan a minimal amount of direct TV broad-casting via satellite, but from themid -1970s onwards US television net-works and Third World governments alikebegan to see the advantages of a satellite -based TV system. And not only the ad-vantages of satellite TV but also thebenefits of secure telephone communi-cations and computer data links of ahitherto unimaginable speed and purity.Again, once the transistor made it possi-ble people began to think of needs theyhad never felt before.

Getting TapedThis kind of self-sustaining growth,

with new developments creating demandand demand calling forth new develop-ments, has been particularly noticeable inthe world of home entertainment over thepast eight -odd years. Wireless and tele-vision we all know about, of course. Butwhat about recorded music? After all, oneof radio's first and greatest conquests inthe late 1 920s was its absorption, for atime at any rate, of the gramophone:previously a scratchy, faint -sounding,clockwork instrument, but transformedby the valve, the wireless loudspeakerand electric drive into a robust, reliablemeans of entertainment. The great suc-cess story of the age, however, was thetape recorder. The idea of recordingsound on magnetic steel wire had beensuggested as far back as 1888. But it wasten years before the Danish inventorValdemar Poulsen took out a US patenton his Telegraphone. This operated bymeans of clockwork -driven spools pass-ing wire through a magnetising/de-mag-netising coil at a rate of 7 feet per second.It was hailed as a major new discoverywhen it appeared on the market andPoulsen set up the American Teleg-raphone Company to sell it, but in the endthe idea came to nothing. The machine'sfrequency response was too poor for useas anything except an office dictaphoneand the wire suffered from an incurabletendency to twist and stretch - as wellas occasionally snapping and slashingaround at high speed until the spools


Feature

Poulsen's "Telegraphone" was patentedin the US in 1898 and used mainly as adictaphone. "Hifi" had yet to beinvented!(British Crown Copyright, Science Museum, London.)

could be stopped. (Wire recording waseventually used for aircraft flightrecorders, because of its robustness, butit was decidedly not bound for the enter-tainment industry.) All the same, interestnever died away completely andpost -1918 AEG, Bell, 3-M and the USNaval Research Laboratories were alllooking into the idea.

In 1928 the German researcherPflumer abandoned wire in favour ofpaper tape coated with iron oxide. Mean-while the Magnetophon company, also inGermany, worked on plastic -based tape.The Blattner system - used by the BBCfor studio recording from 1934 onwards- favoured steel tape which had the dis-advantage of having to be cut with shearsand spot-welded into splices which wentthrough the heads with a deafening clat-ter. But during the early 1930s magnetictape recording was upstaged by thephoto -optical system developed for thetalking films.

Interest picked up once more duringWorld War II, and the German Magneto-phon system began to pull ahead of itsnearest American rival Brush. It wasstrongly sponsored by the German Propa-ganda Ministry, who found its acousticaccuracy and the portability of the tapesvery useful for broadcasting speeches bythe Nazi leadership at times and placeswhich would puzzle Allied intelligence.The result was that by 1945 Magneto -

The modern tape recorder was developedin Germany during World War II, when itwas used to replay and broadcastspeeches by the Nazi leaders.(Photo. Science Museum, London,)

phon tape recorders were way ahead ofanything that the Allies could produce,with a frequency response of up to10kHz. American scientists were highlyimpressed by German recorders capturedat the end of the war, and after severalyears' work to perfect tape -coatings taperecorders began to appear on the USdomestic entertainment market. Mean-while, small battery -powered taperecorders came to replace wax -discmachines in radio outside broadcasting,doing away with the need for a technicianto sit beside the machine while it wasrecording with a camel hair brush to getrid of the swarf thrown up by the needle.The only technological developmentswhich stood between the tape recorderand a mass pre-recorded music marketwere the compact cassette to do awaywith the need for threading the tape (in-troduced by Philips in 19631, and Cr02tape (launched by DuPont five yearslater). Once these were achieved, hificame to be a feature of most householdswith any pretensions to civilisation.

The "Walkman" and similar cassetteplayers probably represent the ultimate inpersonal hifi.

Once sound recording on magnetictape had become an established techno-logy it was only natural that people shouldbegin to think of some better means ofrecording TV programmes than merelypointing a cine-camera at the screen. It isodd to remember, though, that videorecording is an idea as old as televisionitself. In 1930 the Baird Television Com-pany had tried to market shellac videodiscs with its 'Televisor' receivers: nogreat problem in theory, since all the dischad to do was to vary the output of a neonlamp shining through a Nipkow disc ontothe back of a ground glass screen. TheBaird discs turned out to be even less of asuccess than the Televisor itself and sankwithout trace after a few months. It wasnot until 1951 that the Crosby Laborator-ies developed a video recorder whichcould register a TV signal magnetically: inthis case along the length of a tape runn-ing past at over eight feet per second.This method gave tolerable picture qualitybut was so greedy of tape - somethinglike three miles for a half-hour programme- that the idea never made it outside thelaboratory. The first commercially usablevideo system came in 1956 when theAmerican Ampex Corporation broughtout a recorder which entered each picture

frame transversely on a two -inch -widetape. A similar system was taken up bythe BBC under the acronym VERA in thesame year, and between them these twovideo systems dominated broadcast TVfor the next twenty years, even thoughthey were both about the dimensions oftwo wardrobes stuck together, and usedtape spools the size of bicycle wheels.'They gave a very good picture, but theyand the later, smaller, versions of thestudio VTR were clearly out of the ques-tion for the home user.

Helical scanning was developed bySony in the mid -1960s as a compromisebetween tape width, speed and picturequality. It opened the way to a consumervideo market but for some reason -perhaps because people were still absorb-ing hifi sound recording - it failed tocatch on until the late 1 970s when TVaddicts in the USA began to appreciatethe domestic VTR's time -shifting capabi-lities. Suddenly the market exploded as itbecame profitable for the Japanese elec-tronics industry to tool up for mass pro-duction of domestic video recorders. TheAmerican film industry began its belatedshift towards producing for TV and videofirst and the traditional movie theatre se-cond. Meanwhile cable TV, satellite TVand the prospect of fibre -optic cable TVwere starting to follow the way cut by theVTR in fragmenting TV audiences to thepoint where people now speak of'narrowcasting' as the dominant homeentertainment form of the 1980s.

It is only just over a century and a halfsince Faraday made his historic demon-stration of electro-magnetic inductionand only just over a century since Britaingot its first public electricity supply. Dur-ing that time electricity has advancedfrom being a barely understood and notparticularly useful scientific freak to apoint where it is the lifeblood of our civil-isation. A great many of its innovationshave merely helped us to cope with dif-ficulties which we would never have hadin the first place without those same inno-vations - the pocket calculator and thephotocopier are the two examples whichcome readiest to mind - but good thingor not, the technology was there, and so ithappened. The only safe prediction now,in Anno Domini 1982, is that we are onlyseeing the beginning.

A PAM transistor radio dating from1956. As today, the physical size wasdetermined by the need for a relativelylarge loudspeaker.(British Crown Copyright, Science Museum, London.)


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Popular Computing

UNTIL NOW, the only way tocommand our friendly robot has beenby using a ZX81 computer. Now weadd to the list of the controllers ofHEBOT, by publishing anotherinterface; this one lets you operateHEBOT from the keyboard of the BBCMicrocomputer. The interface plugsinto the 1 MHz socket, which is foundon both Model A and Model B.

The interface has exactly the samefacilities as that published inNovember 1982, for the ZX81. It hasan eight -bit data output for controllingthe motors, the pen, the lights and thehorn, and it has a 4 -bit data input forreading the touch sensors. It alsosupplies the power needed foroperating the circuitry of HEBOT,including its motors and solenoid. TheZX81 supplied 10V (or thereabouts),this being the output from the ZXmains adaptor, while the BBC Micro-computer has a nominal 12V outputwhich can supply up to 1A25, andthis is more than enough for HEBOT.Readers who already have HEBOTneed not worry that the power supplyfrom this interface is 1 2V, rather thanthe 10V which little HEBOT has beenused to receiving from the ZX81.Powertran Ltd. who supply the HEBOTII kit, assure me that the motors andsolenoid are in fact rated for 12Voperation, though they work just aswell on 10V. You might find thatHEBOT nips around the room a littlefaster when connected to the BBCMicrocomputer! The other compo-nents in HEBOT are able to work justas well with a 12V supply as with a10V supply, though his eyes may glowthat bit brighter and his voice maybecome that bit stronger. So it looksas if an invigorated HEBOT will soonbe evident!

It is worth noting that this interfacecould also be used to control anyother device instead, provided it workswith an eight -bit TTL input and a four -bit TTL output.

BBC Micro/HEBOT Ow B p

InterfaceHobby Electronics' maestro of the

micros describes a versatile interfacewhich joins the HEBOT II to the BBCMicrocomputer, Model A or Model B,or which can be used for any other

imaginable purpose!

HEBOT Meets The MicroThe interface provides an eight -bitdata output and a four -bit data input,and consists of three parts: theDecoder, which decodes signals onthe address and to the control lines;the Latches, in which data from thecomputer is temporarily stored in sendon to HEBOT; and the input DataBuffers, which receive data fromHEBOT and pass it on to the microwhen asked.

The BBC micro, in common withmost others, has 16 address lines; theupper 8 of these are decodedinternally to produce an output whichgoes by the remarkable name ofFRED. Normally the voltage level onFRED is 'high', but when any of the

256 addresses in the range &FC00 to&FCFF is written to or read from,FRED stops feeling 'high' and feelsrather 'low' instead. This leaves onlythe lower 8 lines (AO to A7) to bedecoded at the interface. The circuitdiagram, Figure 1, shows how theseare decoded by a number of simplelogic gates. The address allotted toHEBOT is &FCFO, which is '11111100 1111 0000' in binary; FREDtakes care of the '1 1 1 1 1100' and theinterface takes care of the '11110000'.

Writing Home to HEBOTThe final gates in the chain take thestate of the Read/Write (R/W) lineinto account. When the micro wants


Popular Computing FROM HEBOT

Figure 1. The full circuit of the BBC/HEBOT Interface.

0C1a

10

A5 0

1 9

IC2cA4 0 9

A3 03

1BMiHsz

A2 0C2a

IClb12

Al 0 3 13

IC2bAO

FRED 0

+12V 0+5V 0

1C1

T1'ovo

7 14

OV Vcc

IC174LS40

IC274LS27

7 14

OV Vc,

IC374LS00

0

IC474LS373

Figure 2. Block diagram of the system.

LOWER ADDRESSBUS 4- FRED + R/W

DECODER

8 16

OV VCC

IC574LS367

2

DATA BUS

DO TO D3

READ

WRITE

DATABUFFERS

DO TO D78 LINES

DATALATCHES

12 13

IC3d

2

TOHEBOT

(ADO' TO D3

IC5

12 14

9

10

+5V

5

1C3cY3---H = WRITE

11

Q4

0706Q5

Q2

03D6.0----VVV- - 00D7441--AAAA - 01

R1-8 1kR

74LS373

OE

047

D6

IC4 D5D2D3

DOD1

7

3

4

LINES

DO TO D78 LINES

SENSORS

CHEBOD

MOTORS

to write to HEBOT, this line is takenlow, consequently the output at pin 8of IC3 (which we have called "WRITE')goes 'high". It is not possible to detectthis high pulse by using a voltmeter,for it lasts only a fraction of amicrosecond, however it is longenough to trigger the latches of IC4.The output of each latch assumes thestate which is present on its datainput line at the instant that WRITEgoes high, and this output levelis fed to HEBOT through resistors R1to R8. Once latched, the outputremains unchanged, even though thedata itself is no longer present on thedata bus. Indeed, the micro may bewriting different data to other partsof its memory but HEBOT's dataremains held at the latches, givingHEBOT plenty of time to respond, andit remains unchanged until a new setof data is written to the latches.

When the micro wants to read datafrom HEBOT's sensors, it addressesHEBOT at &FCFO, as before, but thistime the R/W line is taken "high". Theresult is that the output of IC3 at pin

6 goes low. We call this line .77E75',and when =goes low, it enablesthe data buffers of IC5. In theirdisabled state these buffers havewhat is called a "high impedanceoutput"; in other words, there is a veryhigh resistance (several hundredthousand ohms) between the bufferoutput terminal and the data line. Ineffect, then, the buffer is disconnectedfrom the data line and cannot supplydata to it.

When the buffers are enabled,they have normal TTL outputcharacteristics: if a buffer is receivinga high input from one of the sensorcircuits of HEBOT, the correspondingline of the data bus is made high; ifthe sensor circuit has a low output,that line is low. There are only foursensor outputs from HEBOT, so onlythe lower four lines of the data busare connected to the buffer IC. A hexbuffer (74LS367) was chosen inpreference to a quadruple IC(74LS125) since it has only oneenable input shared between the fourbuffers we are using, whereas the

OV

0 DO0 010 D20 030 D40 D50 D6007,

1 MHzBUS

74LS125 has a separate enable inputfor each buffer, making the wiringmore complicated.

It is feasible to wire up the othertwo buffers to provide a six -bit datainput to the micro, if you like. If youare thinking of giving HEBOT one ortwo additional sensors, take theiroutputs to pins 12 and 14 of IC5,connect the buffer outputs (pins 11and 13) to D4 and D5 and join theother enable input (pin 15) to pin 1.You will also need to remove the trackwhich at present connects pins 12, 14and 15 to the +5V rail.

ConstructionThe interface is built on a double -sided PCB; most of the wiring is onthe under side of the board, but thepower rails and a few linking tracksare on the upper side.

If you are making your own board,take special care that the two designsare exactly registered with each otheron opposite surfaces of the board.There are some "tight squeezes" incertain parts of the board; also thereare 28 points at which the tracks onthe upper and lower surfaces must beconnected and pads are provided inthe design where these connectionsare to be made. Drill a hole throughthe board in the centre of one of thepads; if registration is correct, the drillshould pass through the centre of thepad on the opposite surface. Pass a1mm terminal pin through the holeand solder it to the pads on bothsurfaces of the board. If you want tomake a more professional job of theboard, you can use the special


Popular Computing

'through -PCB' pins which areobtainable from some suppliers, butyou need three proper terminal pins atthe points where the power supplycable is to be connected.

The ICS can be soldered directly tothe board, thus saving cost, though itis advisable to use sockets sinceit is often useful to be able to removean IC when tracing faults. Do notinsert the ICs until all the wiring hasbeen completed and the preliminarywiring checks described below havebeen undertaken.

Connections To The BoardThe interface is joined to the micro bya 34 -way ribbon cable. At the microend, the cable is terminated in a 34 -way Speedbloc connector, which musthave a central key in order to matewith the socket on the micro.Speedbloc connectors are of theinsulation -displacement type and arevery quick to attach to the cable, but avice is essential for this. You alsoneed an adaptor tool (which isinexpensive) but if you lack theequipment, it is far simpler topurchase the cable with the connectoralready attached to one end (seeBuylines).

Note that the diagrams of the 1MHzbus in the BBC MicrocomputerSystem User's Guide are incorrect -at least, those in my copy (issued late

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80mm x 5mm; 34 -way Speedbloccable -mounting socket; 34 -wayribbon cable, approx 60cm; 16 -wayribbon cable, at least 1 m; wire,solder, nuts and bolts etc.

BUYLINESA complete kit of components andparts for the BBC-HEBOT Interfaceis available from Kelan (Hobby -board) Ltd., North Works, Hook -stone Park, Harrogate, NorthYorkshire for £24.00.

KEYS HE171.;-)

FRONT OF KEYBOARD

DISK DRIVE

OV

+5V

NC

O

O 0

O 0

o o

OV

PRINTER

AUXILIARY+12v POWER

_5,yOUTPUT

USER I/O

NOTCH33

ggzszz....gggs=

1 MHz BUS

2

TUBE

FOOT

Figure 3. Schematic view of the connectors underneath the BBC Micro.

1982) are! The diagram of the varioussockets on pg. 499 suggests that the1MHz bus has 26 pins, yet a simplecount shows it to have 34. Thediagram on pg. 503 shows 34 pins,provided that one ignores the ratherodd OV and +5V pins which do notexist on the 1 MHz socket itself. Thenext error is that the numbering ofpins in the two drawings isinconsistent; in this article we adoptthe numbering shown on pg. 503,beginning with pin 1 at the bottom (aOV line) and ending with pin 34 at thetop (address line A7). Once again, weignore the spurious OV and +5V pins.On this reckoning the pin numberingon pg. 499 is wrong in orientation, aswell as in magnitude, and should beas shown on the diagram we publishhere. (We have now learned thatrecent issues of the Guide have beencorrected-Ed.) It is essential tounderstand the pin numbering systembefore you attach the Speedbloc plugand solder the cable to the interfaceboard.

Table 1 shows that HEBOT usesonly 18 of the 34 lines available atthe 1 MHz bus port. Certain of thelines may be cut short at the interfaceend of the cable, as shown in Figure4 but make sure that the cuts areclean, so that there are no thinfilaments of wire protruding from thecut insulation to cause a short-circuitwith an adjacent wire. The sameconsideration applies when you solderthe wires to the board; make certainthat all the strands of each wire gothrough the hole. Examine your workwith a lens when you have finished,looking for single strands lying on thetop surface of the board and pull offany that you see.

Power SuppliedThe power supply for the interfaceand for HEBOT is provided from anoutlet on the underside of thekeyboard. This is marked 'AuxiliaryPower Output' and has a special six -way socket normally used to providepower to the disk drive. The drawingshows which pins to connect, somake sure that you get the orientation

Table 1CONNECTIONS OF THE 1MHz BUS

Line Name Function = usedLifor HEBOT

1

3PVWOV

Read/write strobe

4 1 MHzE 1MHz clock5 OV6 NMI Nonmaskable interrupt

8OVIRO Interrupt request

910

OVFRED Negative strobe FC00-FCFF

1112

OVJIM Negative strobe FDOO.FDFF

1314

OVRST System reset

1516

OVANALOG IN Analogue input

1718

OVDO Data bus, least sig. bit

1920

01D2

Data busData bus

2122

D3D4

Data busData bus

23 D5 Data bus2425

136137

Data busData bus, most sig. bit

2627

OVAO Address bus. least sig. bit

28 Al Address bus2930

A2A3

Address busAddress bus

3132

A4A5

Address busAddress bus

3334

A6A7

Address busAddress bus, most sig. bitof lower byte

Table 1. Correct pin numbering andfunction for the 1MHz bus.

Table 2

BBC 1 MHz BUS

LINE FUNCTION HEBOT CABLE POWER LINES

2 a/Fi BLACK D4 BLUE OV

10 FRED BROWN D1 RED +5V18 DO RED D3 GREY +12V

19 D1 ORANGE D720 D2 YELLOW D621 03 GREEN +12V

22 04 BLUE +12V

23 D5 VIOLET OV

24 D6 GREY OV

25 D7 WHITE D5

BLACK D3'

27 AO BROWN DO'

28 Al RED D2'

29 A2 ORANGE DI30 A3 YELLOW 0131 A4 GREEN DO

32 A5

33 A6

34 Al

Table 2. Summary of the input andoutput connections of the Interface.

correct. You need a three-way cableof about the same length as theribbon cable; connect the other endsof the wires to the three terminal pinsmarked OV, +5V and +1 2V on theinterface board.

The board also provides connectionsfor the 16 -way cable that goes toHEBOT, and this has the same orderof pins as in the ZX81 version. If youalready have a HEBOT tethered to the


Popular Computing

34WAY RIBBONCABLE FROM

MICROCOMPUTER

POWERCABLE FROM

MICROCOMPUTER

31

33

30

29

28

25

24

23

22

20

19

1E

10

RIBBON CABLE TO HEBOT

Figure 4. The component overlay; the component -side tracks of the double -sidedboard are shown in red.

RIBBON CABLE TOBBC MICRO

1MHz BUS

NOTCHEDSUPPORTS

LEAD TOBBC MICRO

POWER OUTLET

MOUNTING THE PCB IN ITS CASE

RIBBON CABLETO HEBOT

Figure 5. The PCB fits neatly into astandard case, but slots must be cutand filed for the ribbon cables.

other end of the cable, do not connectthe it until the wiring has been testedas described in the next section. If youare beginning with a new cable,solder this to the interface board andstrip its wires at the other end, but donot solder it to HEBOT until testing iscomplete.

There are many ways of enclosingthe interface; the simplest method isto mount it in an ABS box ofconvenient size. Certain types of box

have notched strips which slide ingrooves on the inner side of the walls,and this board is of the correct size toslip easily into one of these boxes.Before putting the board in the box,though, cut slots for the cables, asshown in the drawing, and bore ahole for the power cable.

Checking The WiringThere are only five ICs but there aremany connections between them, themicro and HEBOT, so it is well worthwhile making a systematic check forshort-circuits and faulty joints beforeyou attempt to plug the interface intothe micro. Use a multimeter to checkthat there are no short circuitsbetween adjacent wires of the microcable, working your way along therow of pads where the cable issoldered to the board. Similarly, testfor short-circuits where the HEBOTcable is joined to the board.(Alternatively, a variety of PCB -interconnecting plug and socketsystems are available which willresult in a much neater and saferproject. However, they have not beenspecified for the Interface for reasonsof cost, so we'll leave this detail in the

hands of the dedicated constructor.Next, insert the ICs in their sockets

then, using the multimeter as before,check all the connections from theinput cable to the terminal pins of theICs and all connections between theICs themselves. You are a maestro ofthe soldering iron if you do notdiscover at least one dry joint whichcould ruin the operation of theinterface. Similarly, check the powerconnections and, finally, check thatthere is no short-circuit between theOV and +5V line (the interface takesonly 45mA at +5V, so this is wellwithin the capability of the micro'spower output rating).

Testing On The MicroInsert the Speedbloc plug into the1 MHz socket on the underside of themicro and insert the power plug intothe power output socket; have amultimeter handy, set to a voltagescale to read up to +5V. Temporarilyconnect the negative probe of themeter to the OV line of the interface- the pin to which the OV supply lineis soldered will do. Arrange thefurther end of the HEBOT cable on thetable so that the bared ends arespread widely apart, with no chanceof them touching each other! If youhave not yet soldered the HEBOTcable to the board, it will not be aseasy to perform the tests, but youshould be able to manage by makingconnections as required to the farends of resistors R1 to R8, or to thepads for DO' to D3'.

When all is ready, switch on the TVset or monitor, then switch on themicro. If it fails to display itscustomary legend on the screen("BBC Computer...") or the usualbleep from the loudspeaker is notheard, switch off immediately; youhave probably still got a short to oneof the address or data lines. Go backand retest the interface, butthoroughly this time!

As explained in the section onaddressing, the interface is placed ataddress &FCFO (64752 in decimal),and we treat the interface as a singlebyte in memory, writing data into it orreading data from it. To test output tothe interface, first type:

H = &FCO

then press 'Return'. This sets variableH to the address of the interface(better to refer to it as the address ofHEBOT, since eventually HEBOT willbe attached to the interface). Nexttype:

?H = &FF

then press 'Return'. This commanduses the Indirection Operator, '?". asexplained on pg. 4u9 of user sManual, to write 'FF' into HEBOT'saddress. In binary, 'FF' is '1111 1111',so we shall expect that all 8 outputsof the latch IC will now be 'high'. Usethe testmeter to measure the voltageat the HEBOT cable end for all of lines


Popular Computing

DO to D7, but do not expect to read+5V, even though we often equate'high' with this voltage. In practice,anything over +2V is 'high' to a TTLIC! Now key in:

?H = &O

then press 'Return'. There is no needto repeat 'M = &FCFO' unless youhave switched off the micro orinadvertently pressed 'Break'. Afterthis, all the outputs DO to D7 shouldbe low, (less than OV8). If any linefails to go 'high' on the first commandand 'low' on the second, switcheverything off and re-examine theboard for faults, concentratingparticularly on the faulty line.

For a final check on output, trywriting other values to the HEBOTaddress. For example, if you key '?H=&AA' you are sending the bit pattern'1010 1010', ie the even numbereddata outputs are 'low' while the odd -numbered ones are 'high'. Now to testthe input side. The command for thisis:

PRINT ?H

then press 'Return'. It is handy to setup one of the user -defined functionkeys to do this. The command causesa decimal number representing theinput state of all eight data lines to beprinted on the screen. Thus the valuesprinted normally range from 0 (00000000, all lines 'low') to 255 (11111111, all lines 'high').

However the output from HEBOT ispresent on only the lower four datalines so when reading from HEBOT,there is nothing connected to theupper four data lines. A line with noinput reads as 'high' so D7 to D4always produce '1111'. Thus therange of values obtained by testingHEBOT lies between 240 (1111 0000)and 255. If all of the lines DO' to D3'are left unconnected, then all linesare effectively high, and '255' appearson the screen. Now connect line DO'to the OV rail and key the commandagain. You should see '254' this time,for the data input is '1111 1110'. Tryvarious other input combinations,grounding one or more lines of DO' -D3'! If you convert the number on thescreen to its binary form, the '0'scorrespond with a grounded datainput.

InterferenceYou may find that sometimes thevalue you get on the screen is lowerthan expected. In particular, it may be16 less than expected. This is due to a'low' appearing on data line D4. Now,this cannot be coming from theinterface in the normal way, for theinterface has no output to line D4 orany of the upper lines.

This 'low' is due to electromagneticinterference between adjacent wiresin the cable, and becomes moreevident the longer the cable; it wouldhave improved matters if the 1 MHzbus had had grounded (0V) linesalternating with each data line andaddress line. The diagram on pg. 505of the BBC Manual shows that there

are such grounded lines on part of thebus (between lines carrying controlsignals), but not on the part carryingdata and addresses. Grounded lineswould have shielded wires from thisinterference and though the lack ofshielding does not matter normally(for most interfaces would be sendingfirm data along every line of the bus),with this interface the upper fourlines are left 'floating' and prone topick up any interference which isaround.

Fortunately it is no problem toprogram the micro to ignore the upperfour data lines completely, as in line90 of Program 1. In transmission ofdata to the interface, interferencedoes not occur, for none of the linesare 'floating'.

If, in the tests above, you find thatany combination of the lower fourdata inputs does not produce thecorresponding figure on the screen(ignoring odd effects of interferenceon the upper four lines), switch offand re-examine the interface board,especially the line which is givingtrouble. Assuming that all nowappears to be in working order, switchoff, and make the connections toHEBOT.

PROGRAM 1 "Walk and Avoid"

10 REM " HEBOT's MOVE "20 HEBOT = &FCFO: REM HEBOT's address30 Collision = FALSE: REM Not colliding yet40 Motion = 5: REM forward50 7HEBOT = Motion: REM HEBOT to move60 PROCdelay(.2): REM move for .2 secs70 7HEBOT = Motion - 16: REM move and flash lights80 PROCdelay1.21:REM for .2 secs90 Sensors = 7HEBOT AND 15: REM test sensors

100 IF Sensors <> 0 THEN 140: REM in collision!110 IF Collision = TRUE THEN 180120 Emergency = INKEY(50). REM any key pressed?130 IF Emergency '"0 THEN 7HEBOT = 0: STOP, ELSE 50140 IF Sensors := 6 THEN 190150 Motion = 10 64:REM to back and sound horn160 Collision = TRUE: REM in collision170 GOTO 50: REM to move back180 Collision = FALSE: REM reset flag190 ?HEBOT = 8: REM turn left200 PROCdelay(1):REM turn for 1 sec210 GOTO 40: REM to move forward again300 OEF PROCdelay(secs)310 TIME = 0320 REPEAT330 UNTIL TIME secs 100340 FNDPROC

PROGRAM 2 "Recorded Moves"

10 REM " Recorded moves ''20 HEBOT = &FCFO. REM HEBOT's address30 15138 = 32:REM set 'Caps lock' mode40 data = 0: REM HEBOT stopped50 7HEBOT = data60 motionS = "S"70 last motions "S"80 INPUT"How many moves",moves90 DIMmoves(rnoves)

100 DIMtimes(moves)110 PRINT:PRINT"HEBOT is under your control. -120 PRINT"Use keys F, B. R. L. or S."130 FOR J = 1 TO moves140 TIME = 0150 PRINT"Key move no. ";J160 motionS = GETS:REM welt for key170 F motionS = last motionS THEN 160:REM no change of key180 F motions = "S" THEN data = 0:GOTO 240: REM stop490 F motionS = "F" THEN data = 5:GOTO 240: REM forward200 F motionS = "B" THEN data = 10: GOTO 240 REM back210 F motions = "L" THEN data = 9:GOTO 240: REM left220 F motions = "R" THEN data = 6:GOTO 240: REM right230 GOTO 160(REM invalid key pressed240 7HEBOT = data: REM instruct HEBOT250 moves(J) = data: REM store move260 times(J-1) = TIME:REM store time270 last motions = motions280 NEXT J290 PRINT"Preas S to stop HEBOT"300 IF GETS<" "5" THEN 290310 ?HEBOT = 0: REM stop HEBOT320 times(moves) = TIME330 PRINT:INPUT"How many repeats".repeats340 FOR K = 1 TO repeats350 PRINT"Repetition no. "A<360 FOR J = 1 TO moves370 PRINTTAB(18)"Move no. ";J380 TIME - 0390 7HEBOT = moves(J)400 REPEAT410 UNTIL TIME = times(J)420 NEXT J430 NEXT K440 PRINT:PRINT"That's alll"450 END

Two HEBOT programs in BBC BASIC.

Programming HEBOTThe tables on pg. 11 of the November1982 issue of HE summarises theways of commanding HEBOT andreading from the sensors, and exactlythe same arrangement of data lines isused in this interface. The programsin that issue are in Sinclair BASIC;

'here we list equivalent programs inthe BBC BASIC, which differs in anumber of respects from SinclairBASIC. The first program is the 'walkand avoid' routine, in which HEBOTmoves forward, eyes flashingmenacingly until it runs into anobstacle. Muttering under its breath(or rather, tooting vociferously on itsspeaker) it backs away, turns left andthen procedes in a forward directionagain. Those of you who have seenthe pond animal, Paramecium (or anyof its relatives), alive under themicroscope, will know just howHEBOT behaves with this program.

The second program allows you totype in a sequence of commands andthen run the program so that HEBOTcarries them out in order; the microhas plenty of memory to spare so avery large number of movements canbe programmed if you wish. You canuse a variant of this program to makeHEBOT draw a pattern on a sheet ofpaper, or with a little ingenuity, youcould program HEBOT to dance tomusic produced by the micro's soundgenerators. The routine can berepeated or not, as selected by yourentry at the beginning of the secondphase.

With the 16K of the Model A or the32K of the Model B at your disposal,there is massive scope forprogramming HEBOT. It can learnhow to run a maze. Or it can beallowed to wander around the room atrandom, bumping into objects andmemorising their positions; thisinformation, stored in the computercan be used to build up a map of theroom, for display on the screen.Another project is to program HEBOTto write its own signature on a largesheet of paper. It can learn to writetoo; you type a message in at thekeyboard and HEBOT writes it out onpaper. These are only a fewsuggestions of things that HEBOT canbe programmed to do.

On pg. 435 of the User's manual,Aunty Beeb takes on her mostseverely admonitory tone andthreatens dire results if we 'insist' onaddressing HEBOT directly, instead ofusing Aunty's OSBYTE calls. Sorry,Aunty, but this programmer insists (asyou put it) on addressing HEBOTdirectly. As you point out in anafterthought, the required OSBYTEroutine is not available before ROMrelease 1.0, so many of our readershave no other option but directaddressing! And those lucky few whoeventually use the Tube would reallynot find it all that difficult to modifytheir program accordingly.Apple owners take heart - we willshortly be publishing an interface foryou! HE


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D.P. [ON -ON] @ £0.72 eachD.P. [ON -OFF -ON] @ £0.78 each

For full productlist, send s.a.e.

**SPECIAL OF FE R** 1 off each only £3.00 includingp/p & VAT. Send cheque or P.O. to:

SELECT COMPONENTS LTDSTAMFORD HOUSE, STAMFORD NEW ROAD

ALTRINCHAM, CHESHIRE WA14 1BL

VARIABLE VOLTAGE POWER SUPPLIES MULTIRAIL POWER SUPPLIES FOR1 - 30v 1.5A £38.75 0 - 30v 1.5A f39.991 - 30v 3A £42.99 0 - 30v 3A £44.50 MICROS ETC.1 - 30v 5A £45.75 0 - 30v 5A . E47.801 - 30v 10A £55.99 0 - 30v 10A E58.99

CONSTANT VOLTAGE/CONSTANTCURRENT SUPPLY1 - 32V/100mA - 5A £55.90

HIGH EFFICIENCY SWITCHING POWERSUPPLY2 - 32V 4A Max £52.99

ALL THE ABOVE SUPPLIES ARE FITTED WITH QUICK -FIT METERS. IF MORE ACCURATE METERING ISREQUIRED PLEASE ADDE E3.00. FOR DIGITALMETERING ADD £15.

NICAD CONSTANT CURRENT CHARGER FOR ALLDOMESTIC BATTERIES E19.99

5v 5A, - 5v IA, 12v IA, Ad 1A, 24v 1A £34.50

IEv HAS CROWBAR OVERVOLTAGE PROTECTION)

OTHER SUPPLIES FOR MICROS

5v 3A £25.99 5v 5A £28.99 5v 10A E35.9912v 1A E12.45 12v 3A E27.95IALL THE ABOVE HAVE CROWBAR OVER VOLTAGE PROTECTION,

1 - 15v 3A E27.99 1 - 15v 5A E34.99- 2 - 15v 3A..........£29.99 - 2 - 15v 5A___._£35.99SWITCHMODE P.S.U. 5v 5A E35.75

C.B. RADIO E.T.C. POWER SUPPLIES12v/13.8v 3A E19.99 12v/13.8v 5A E25.9912v/13.8v 10A E34.99

IALL WITH CROWBAR OVERVOLTAGE PROTECTION,

S.A.E. FOR LISTS

ALL POWER SUPPLIES ARE FULLY STABILISED AND OVERLOAD PROTECTED. ALL PRICES ARE INCLUSIVE AND INCLUDE CARRIAGE

EDWARDS ELECTRICUNIT 3, MILL LANE, CHURCH STREET, BRIDGWATER, SOMERSET TA6 5AT

It's easyto complain

aboutadvertisements.

The Advertising Standards AuthorityiIf an advertisement is wrong.we're here to put it right.

A S A Ltd. Brook Hni tse Torrtngton Place. London WCIE 7HN

1113tMARCO

TRADINGBILIINIS

111611 STRUTWIY

TEL 1111111131133113

GOT YOUR

LATEST COPY

YET???

Our 72 page fully illustratedcatalogue includes special offer

lists, order forms, and pre -paid envelopes and lots lots more.To obtain your copy of Marco Trading's latest catalogue send35p plus 26p postage to:Marco Trading, Dept H92, The Maltings, High Street,Wem, Shropshire, SY4 5EN. Tel: 0939 32763


15b Lower Green,Poulton-le-Fylde,BLACKPOOL,Lanes FY6 7JL

Tel: (0253) 885107

We are only small, but our aim is to please, and our stock range is growingall the time. If any of the following interests you: -

TRANSISTORS - DIODES - CMOS - TTL - TTL LS - LINEAR ICs -RESISTORS - POTENTIOMETERS - CAPACITORS - VE ROBOARD -

VE ROBOXES - INSTRUMENT CASES - TRANSFORMERS - FUSES -

GSC BREADBOARDS - SOLDERING IRONS - ETC, ETC.

Please send a stamped addressed envelope or call in for a copy of our 16 -

page price list.

r MAKE YOUROWN P.C.BS.

WelOt.

DIRECT ETCH KITCOPY DIRECT FROM MAGAZINE or OWN DESIGNSimple system - Complete kit containing PCB, PatternTransfer & Etch Resist Sheets, Tray & Etchant, CopperCleaning Block, Gloves & full instructions. £15.60

Price inclusive of VAT & carriage. Please allow 21 daysfor delivery. Cheques, PO's or signed Access orders welcomed.

complete P.C.B. workshop

a division ofKELAN ENGINEERING LtdHookstone ParkHarrogate. N. Yorks

jHB/PC1

MASTER ELECTRONICS NOW!The PRACTICAL way!

This new style course will enableanyone to have a real understandingof electronics by a modern, practicaland visual method. No previousknowledge is required, no maths, andan absolute minimum of theory.

You learn the practical way in easysteps mastering all the essentials ofyour hobby or to start or further acareer in electronics or as a self-employed servicing engineer.

All the training can be carried out inthe comfort of your own home and atyour own pace. A tutor is available towhom you can write personally at anytime, for advice or help during yourwork. A Certificate is given at the endof every course.

You will do the following:Build a modern oscilloscopeRecognise and handle current electronic

componentsRead,draw and understand circuit diagramsCarry out 40 experiments on basic

electronic circuits used in modernequipment

Build and use digital electronic circuitsand current solid state 'chips'

Learn how to test and service every typeof electronic device used in industry andcommerce today. Servicing of radio, T.V.,Hi-Fi and microprocessor/computerequipment.

Newebb?NewCareer?NcwHobby?Get into Electronics Now!IPATi

Please send your brochure without any obligation toNAME

ALARMSFREE CATALOGUE!

OUR GREAT NEW ILLUSTRATED CATALOGUE ISPACKED WITH INFORMATION ON SUPERBQUALITY, PROFESSIONAL BURGLAR ALARM

EQUIPMENT---- AT UNBEATABLE PRICES!

SEND S.A.E. OR PHONE NOW A.D. ELECTRONICS

FOR YOUR COPYDEPT. HE3

rtituciitcx 217 WARBRECK MOORTHIEFCHECK BURGLAR MAIN AINTREE LIVERPOOLALARM 111-Y SYSTEM DISTRIBUTOR L9 OHUI051 523 8440

ETESON ELECTRONICS

EZEZ

I am interested in:1 I COURSE IN ELECTRONICS

as described aboveADDRESS RADIO AMATEUR LICENCE

I MICROPROCESSORS

I BLOCKr -I LOGIC COURSECAPS PLEASE

HE/5/821

OTHER SUBJECTS I

! PiaishNationalRadio8cElectronics School Reading, Berks. RG I 7BR

70 hobby Electronics, May 1983

PRINTED CIRCUIT BOARDS (PCBs) for HE projects have often represented anobstacle for our readers. Some of you, no doubt, make your ownbut our PCB Service saves you the trouble.NOW you can buy your PCBs direct from HE. All (non -copyright) PCBs will be availableautomatically from the HE PCB Service. Each board is produced from the same master asthat used for the published design and so each will be a true copy, finished to a high stan-dard.Apart from the PCBs for this month's projects, we are making available some of thepopular designs from earlier issues. See below for details. Please note that only boards forprojects listed below are available: if it isn't listed we can't supply it.

..............SERVICE(Reveyarnade ForPi /eaders i

..........

March 81 February 82 HE/8209/3 ZX Interface £3.34HE/8103/1 Steam Loco Whistle £2.65 HE/8202/1 Relay Driver £2 07 HE/8209/4 Slot Car Controller £1 98

April 81HE/8104/1HE/8104/2

Super SirenRussian Roulette

Game

£1 97

£1.60

HE/8202/2

March 82HE/8203/1

Mast -Head Amp £1 08

Digital Dice £1 40

October 82HE/8210/1HE/8210/2

HE/8210/3

Flash Point AlarmNegative Voltage

GeneratorSquelch Unit

£2.13

£1.49£2.52

May 81HE/8105/1 Voice Operated

Switch £1.67

April 82HE/8204/1 Digital Capacitance

Meter £4.02November 82HE/8211/1 Pedometer/

HE/8105/2 Organ 1 £4.64 HE/8204/2HE/8204/3

Dual Engine Driver £3.27Bike Alarm £2.45

Odometer £2.13

June 81HE/8106/1HE/8106/2

Envelope GeneratorOrgan 2

£1.87£2.53

May 82HE/8205/1&2 Digital Thermometer

(Set of Two) £4.62

December 82HE/8212/1HE/8212/2HE/8212/3&4

Phase FourMicrologTape/Slide

£2.83£3.98

July 81 HE/8205/3 Echo-Reverb £5.63 (Set of Two) £5.26HE/8107/1 Organ 3 £6.00 HE/8205/4 Cable Tracker £1.85 HE/8212/5 TV Amp £5.70HE/8107/2 Organ 4 £6.00 HE/8212/6 Lofty £2.61HE/8107/3 Ultrasound Burglar

Alarm £2.53 June 82HE/8212/7HE/8212/8

Noise GateLow Cost Alarm

£3.60f 2.30

HE/8206/1 Power SupplyAugust 81HE/8108/1HE/8108/2

RPM MeterThermometer

£1.77£1 67

Design £2.48HE/8206/2Auto-Wah £3.08HE/8206/3 Auto Greenhouse

Sprinkler £3.45

January 83HE/8301/1HE/8301/2

Chip ProbeSwitched Mode

Regulator

£1.82

£1.96September 81HE/8109/1 Power Pack £1 69

HE/8206/4&5 Telephone Timer(Set of Two) £6.50 February 83

HE/8302/1 Incremental Timer £7.13HE/8109/2 Reaction Tester HE/8302/2 DigiTester PSU £6.70

Game £1 71 July 82HE/8109/3 'Diana' Metal HE/8207/1 Tanover £2.13 March 83

Detector £3.31 HE/8207/2 TVI Filter £1 .78 HE/8303/1 LoudspeakerHE/8207/3 Computer PSU £7.68 Protector £2.51

October 81 HE/8207/4 Solar Radio £1.98 HE/8303/2 Overvolt Cutout £2.25HE/8110/1 Combination Lock £2.65

November 81HE/8111/1&2

December 81

Sound Torch(Set of Two) £5.31

August 82HE/8208/1&2

HE/8208/3&4

Digital Millivoltmeter(Set of Two) £4.34

Audio Analyser(Set of Two) £11.55

April 83HE/8304/1HE/8304/2&3

HE/8304/4

6502 EPROMMERDucker

Main BoardPreamp Board

Power Down

£7.18

£3.56£2.31£2.10

HE/8112/1 Pedalboard Organ £5.64September 82 May 83

January 82 HE/8209/1&2 Signal lights HE/8203/1 BBC Interface £4.82HE/8201/1 Intelligent NiCad Main Module £1.96 HE/8305/3 Stall Thief £2.50

Charger £2.83 Junction Module £ 1 .70 HE/8305/4 Auto -Test £2.50

PLACE an order for your PCBs using the form below (or a piece of plain paper if you prefer not tocut the magazine), then simply wait for your PCBs to drop through your letterbox, protected bya Jiffy bag.

HE PCB Service, Argus Specialist Publications Ltd, 145 Charing Cross Road, London WC2H OEEI enclose a cheque/Postal Order made payable to ASP Ltd, Boards Required Pricefor the amount shown below Price.ORI wish to pay by Barclaycard. Please charge my account number

VISAOR

I wish to pay by Access. Please charge to my account number

SIGNATURE

NAME(BLOCK CAPITALS)

ADDRESS(BLOCK CAPITALS)

Add 45ppErp 0.45

Please allow 21 days for delivery Total Enclosed £


PCB FOILPATTERNS

Top right; the HE Lofty' PCB, which was not published with the project.Middle right; the Auto -Tester PCB.Bottom right; the foil pattern for the Stall -Thief.Above top; the component side tracks for the BBC/HEBOT Interface.Above, the main foil pattern.

0 0

0

O CAN ANTI -THEFT DEVICEHE

483

7O

0

0

0


FOR SALE

SLIM COMBINATION -Stainless steel pen, & quartzL.C.D. watch, uses 'Parker' refill,instructions. Only £3.99. (sparebattery 50p) Two for only £5.99!Taits Mail Order (Dept. HE) 31Lime Grove, Addlestone,Surrey.

KIA return an AD No 6100 Watt fibreglass power -amplifiers + to 3 heatsinking(£19.95p) - Ready to play +data ... Post advert + £6.95p -8 Cunliffe Road, Ilkley.

ACORN ATOM 12K + 12KPSU, VIA, LEADS, MANUALsoftware, including CHESS,INVADERS. Excellent condi-tion. £180 - Crayford 528264

POWERFUL SW Medium FMportable radio, only £14.95 p+p £2.55. Sharland Enterprises,7 Mountview, Mill Hill NW73HT.

L.C.D. PENWATCH 5 -Funchon S/Steel takes Parkerrefills. Guaranteed only £2.99+ 35p p + p spare battery. Add50p Ashley Sales, 7 BeverleyGardens, St Albans, Herts AL49BJ.

COMPONENTS

BUMPER BOX OF BITSWOW!! We'vegot so manycomponentsin stock, we can't possibly list them all!!- So buy a box, in it you'll find resistors,capacitors, displays, switches, panelswith transistors, diodes, IC's, etc., coils,pots ... and so on. All modern parts -guaranteed at least 1000 items.Minimum weight 10Ibs. ONLY £8.50inc.

ELECTRONICS WORLD1F Dews Road Salisbury Wilts SP2 7SN

COMPONENTS

ELECTRONICS componentsshop in MAID -STONE, KENT!Thyronics Control Sytems, 8Sandling Road, Maidstone,Kent. Maidstone 675354.

ALL NEW COMPONENTSC-MOS 4012-8p, 4017-25p, 4019-14p,4022-32p, 4023-12p, 4024-20p, 4025-12p,4049 -18p, 4071-12p, 4076-28p.4081-10p, 4518-28p, 4520-260, 4528-34p. 4557-140p, NE567-38p, SPX6-20p,314A223 -4p. TTL 7400-60, 7404-8p,7412-8p, 7419-14p, 7414-20p, 7416FJ-12p, 7495-24p, 74L592 -24p.

30p P&P order under £6. No VATV Bansal, 14 Davlgdor Road, Hove,

Sussex BN3 100. Tel (0273) 732419

DIGITAL WATCH REPLACE-MENT parts. Batteries, dis-plays, backlights etc. Also re-ports, publications, charts.S.A.E. for full list. Profords, Cop-nersdrive, Holmergreen, BucksHP1 5 6SGE.

WSW -SANDIAuto Electronics,

103 Coventry Street,Kidderminster

Tel: (0562) 2179Brand new components byreturn post or ring withAccess/Barclaycard numberfor same day despatch.

All manufacturers guaran-teed new stock. All at mostcompetitive prices. Cata-logue available only 50p. Allprices inclusive of VAT.

BOOKS & PUBLICATIONSHOBBY ELECTRON ICSMAGAZINE. Opportunity topurchase volumes one to four.Mint condition. Offers? Cray -ford 526380.

ELECTRONICS BOOKS.International publishers.Lowest rates. Ask list. Businesspromotion. 376 LajpatraiMarket Delhi India.

ADVERTISEMENTRATES Semi -Display (min 2 cms)1-3 insertions £7.50, per cm6-11 insertions £7.00 per cm12+ insertions £6.50 per cmLineage 26p per word (min 15 words)Box Nos. £2.50Closing date 2nd Friday of themonth preceding publication date.All advertisements in this section must be prepaid.Advertisements are accepted subject to the terms andconditions printed on the advertisement rate card(available on request)Send your requirements and cheque/P.O. to:

HOBBY ELECTRONICS CLASSIFIEDADVERTISING, 145, CHARING CROSS RD,LONDON WC2H OEE

SPECTRUM journal Microzine9k cassette £1 payable S.Brown 86 Bronson Road Lon-don SW20 8DY

KITSELECTRONIC kits for sale:Morse Practice £4.10, Dice£8.10. SAE for details. Bee Mic-ro, 33 Bevendean Crescent,Brighton, E Sussex.

PRINTED CIRCUITS. Makeyour own simply, cheaply andquickly! Golden Fotolac light-sensitive lacquer - nowgreatly improved and verymuch faster. Aerosol cans withfull instructions, £2.25. De-veloper 35p. Ferric chloride55p. Clear acetate sheet formaster 14p. Copper -clad fib-reglass board, approx. 1mmthick £1.75 sq. ft. Post/packing75p. White House Electronics,Castle Drive, Praa Sands, Pen-zance, Cornwall.

HAVEN HARDWAREZX81 £49.90. Inverse Video £4.50. Re-peating Keymodule £5.95. ZX Spectrumsoftware: Repulser fruit machines andSolitair £4.95 each. Mancala and Patience£5.95 each. Jupiter Ace £89.90. InverseVideo £4.95.

Access taken. SAE for details.HAVEN HARDWARE

4 Asby Road, Asby, Workington,Cumbria Tel: 094-686 627Agency enquiries welcome

EQUIPMENT

EQUIPMENT

BURGLAR ALARM EQUIP-MENT. Please visit our 2,000sq. ft. showrooms or write orphone for your free catalogue.C.W.A.S. Ltd. 100 RooleyAvenue, Bradford BD6 1DB.Telephone 0274-308920.

BURGLAR ALARM EQUIP-MENT: As used in the trade forDIY. JN Security Centre, 176Sydenham Road, LondonSE26 5JZ. Tel 01-778 1111Showroom open six days.

HIGH POWER MERCURYION LASER, emits green/redlight. Easily built bythe amateurconstructor. Ideal school pro-ject etc. comprehensive kit ofplans, including source of allmaterials. £5.25 + 25p p&p.Lastertech, 31 Mill Brow, Chad-derton, Lancs.

CENTURIONALARMSWe manufacture,you save £ £ C's

Send s.a.e. or phone for ourFree list of professionalD.I.Y. Burglar Alarm Equip-ment and accessories.Discount up to 20% off listprices, eg. Control Equip-ment from £15.98, DecoyBell Boxes from £5.95 inc.

TRADE ENQUIRIES WELCOME

0484-21000or

L44355A27Fi2M4S hr.r (8E711)CENTURION

265 Wakefield Road. Huddersfield10/405 9BE, W. Yorkshire

Access 6 VisaOrders Welcomed

TELEQUIPMENT. Type 55Dscope dual beam separate XYamp etc. Slight screen burnotherwise perfect. Sensibleoffers 01-428 6089

U.V. Light exposer unit foruse in prep. of Photo -resistP.C.B's. Attractive wooden con-struction with exposer area of250 x 150mm. Case 350x250x-95mm 240V operation. Only£37.00 p&p. Send cheque toV.E.P. Ltd., 5 Hewens Road,Uxbridge, UB10 OFR.

AERIAL AMPLIFIERS Im-prove weak television re-ception. Price £6.70. S.A.E. forleaflets. Electronic Mailorder,Ramsbottom, Lancashire BLO9AGH.


EQUIPMENT

Nascom Spares

Nascom I PCB & Parts list and 3 AMPPSU.PCB £15 each £1 p&p. Nascom ImpMain Drive plus printing head, base paneland PCB £25 £2.50 p&p. Toroidal trans-former8 amp& 15-0-15volt 2 amp£ 25 £3p&p.Transformer 14-0-143.2a£5 £2 p&p.Panel meter 7cmx7cm 1 ma F.S.D. (new butneeds rescaling). £2.50 , 50p p&p. Exequip. Imp board Contains 280 P10 CPUUARTetc C6. £1 p&p. 20 wayRainbow Rib-bon with 1 I.D.C. header 30" long f 1 25pp&p. Dyonics 17, Hawkesworth Drive,Kenilworth, Warwickshire, CU8 2GP.

Please add 15% VAT to all ordersSAE for further parts list.

NEW 1983 EDMUND SCIENTIFICCATALOGUE NOW AVAILABLE

72 pages of.- Solar Energy. Health,Holography, Lab. Equipment, Astronomy,Fibre Optics, Photography, Motors,Weather, Magnifers, Magnets, And More,

Sand for FREE copy to:- Dept HE 10,Rhelnbergs Sciences Ltd., SovereignWay, Tonbridge, Kent TN9 1 RN orphone 0732 357779

Ultra -violet exposure units.Print your own photo -etchP.C.B's and enjoy the freedomof being able to change yourcircuits without ruining hoursof artwork U.V. - 300 unit(240x150mm area/2x8 watt)-£35.00 plus VAT. U.V. - 800unit (240 x 350mm area/4 x 15watt) - £85.00 plus VAT. TheU.V. 800 is controlled by anelectronic precision timer.Prices include UK postage.Available direct from manufac-turers. Electronics AssistanceLtd., Unit 1, Brynberth Indus-trial Estate, Rhayader, PowysLD6 5EN. 0597-810711.

ADD ONS

Teletext (Oracle/Ceefax)add-on adaptors for any televi-sion. Only £149.95 inclusive.Also Prestel/Viewdata andTelesoftware. Cytel (HE),FREEPOST, Bristol BS10 6BR.(0272) 502008 anytime.

SOFTWARE GAMES

SPY CASSETTE. Amazingcassette will allow you to stop,list or copy any previouslyunstoppable tape. Includestwo free utilities. State if forZX81 or Spectrum. Send just£3. Bobker, 29 ChaddertonDrive, Unsworth, Bury, Lancs.

PLANS 'N DESIGN

AMAZING ELECTRONICPLANS. Lasers, Super -powered Cutting Rifle, Pistol,Light Show, Ultrasonic ForceFields, Pocket Defence Weap-onry, Giant Tesla, Satellite TVPyrotechnics, 150 more pro-jects. Catalogue £1 (refund-able) - from Plancentre,Bromyard Road IndustrialEstate, Ledbury HR8.

WANTED

WANTED Part number formeter. Heathkit MultimeterMM -1 U or supply meter. Con-struction. Books. Circuit etc.Please Telephone Stevenage(0438) 52789.

PARAPHYSICS JOURNALRussian translations). Psychot-ronics, Kirlianograph, heri-phonic music, telekinetics.Computer software. SAE -4x9" - Paralab, Downton,Wilts.

SOFTWAREAPPLICATIONS

SPY CASSETTE. Amazingcassette will allow you to stop,list or copy any previously un-stoppable tape. Includes twofree utilities. State if for ZX81 orSpectrum. Send just £3 Bob-ker, 2.9 Chadderton Drive,Unsworth, Bury, Lancs.

HOBBY ELECTRONICSCLASSIFIED ADVERTISEMENT - ORDER FORM

If you have something to sell now's your chance! Don't turn the page - turn to us!Rates of charge: 26p per word per issue (minimum of 15 words). Box Nos. £2.50and post to HOBBY ELECTRONICS, CLASSIFIED DEPT., 145 CHARING CROSS ROAD, LONDON WC2PLEASE INDICATE HEADING REQUIRED

£3.90

£5.20

£6.50

£7.80

£9.10

£10.40

£11.70

£13.00

Please place my advert in HOBBY ELECTRONICS for issues commencing as soon as possible.I am enclosing my Cheque/Postal Order/ International money Please use BLOCK CAPITALS and include post codes.Order for (delete as necessary) (Made payable to A.S.P. Ltd) Name (Mr/Mrs/Miss/Ms)

(delete accordingly)AddressOR Debit my Access/Barclaycard

(Delete as necessary)

Signature Date

All classified advertisements must be paid for 'n advance. Daytime Tel. No.

IV


TYPE 'C'

MULLARD SPEAKER KITSPurposefully designed 40 watt R.M.S. and Xwatt R.M.S. 8 ohm speaker systems recentlydeveloped by MULLARD'S specialist team inBelgium. Kits comprise Mullard woofer 18" Of51 with foam surround and aluminium voice coil.Mallard 3" high power domed tweeter. B.K.E.built and tested crossover based on Mullardcircuit, combining low loss components, glassfibre board and recessed loudspeaker terminals.SUPERB SOUNDS AT LOW COST. Kits suppliedin polystyrene packs complete with instructions.8" 40W system - recommended cabinet size 240x 216 x 445rnmPrice £14.90 each + £2.00 P & P.5" 30W system - recommended cabinet size160 x 175 x 295mmPrice E13.90 each a- E1.50 P 9 P.

Designer approved flat pack cabinet kitsincluding grill fabric. Can be finished with iron orveneer or self adhesive vinyl etc.8" system cabinet kit 18.00 each + 12.50 P & P5' system cabinet kit £7.00 each + E2.00 Pb P

STEREO CASSETTE TAPE DECK MODULE.Comprising of a top panel and tape mechanism coupled toa record/play back printed board assembly. Supplied asone complete unit for horizontal installation into cabinet orconsole of own choice. These unite am brand new, readybuilt and tested.Features: Three digit tape counter. Autostop. Six pianotype keys, record, rewind, fast forward, play, stop andeject. Automatic record level control. Main inputs plussecondary inputs for stereo microphones. InputSensitivity: 100mV to 2V. Input Impedance: 68K.Output level: 400mV to both left and right handchannels. Output Impedance: 10K Signal to noiseratio: 45dB. Wow and flutter: 0.1%. Power Supplyrequirement.: 18V DC at 300mA. Connections: Theleft and right hand stereo inputs and outputs are viaindividual screened leads. all terminated with phone plugs(phono sockets provided). Dimensions: Top panel 51in

111in. Clearance required under top panel 21in.Supplied complete with circuit diagram and connectingdiagram. Attractive black and silver finish.Price 125.70 a- 12S0 postage and packing.Supplementary parts for 18V D.C. power supply(transformer. bridge rectifier and smoothing capacitor)13.50.

dt80 LOUDSPEAKER

The very best in quality and value. Portedtuned cabinet in hardwearing black vynide wit

protective corners and carry handle. Built andtested, employing 10in British driver and Piez.tweeter. Spec: 80 watts RMS; 8 ohms; 45Hz20KHz; Size: 20in x 15in x 12in; Weight: 30

Pounds.Price: £45.00 each. BO per pairCarriage: 5 each. £7 per pair

UDSPEAKERS15" 100 watt R.M.S. P.A., DISCO,BASS GUITAR) Die cast chassis, 2"aluminim voice coil, white cone withaluminium centre dome. 8 ohm imp., Res.Freq. 20Hz., Freq. Reap. to 2.5KHz., Sens.97dB (As photograph). Price: E32.00 +123 carriage.12" 100 watt R.M.S. )HI-FI) Die castchassis. 2" aluminium voice coil. Blackcone. 8 ohm imp., Res. Freq. 20Hz., Freq.Resp. to 4.5KHz. Sens. 95dB. (Asphotograph). Price: £23.50 + E3 carriage.W' 50 watt R.M.S. IHI-FI, P.A.) I %,"aluminium voice coil. White cone."8 ohmimp. Res. Freq. 40Hz., Freq. Resp. to 6KHz.Sens. 92dB. Also available with black conefitted with black metal protective grille. (Asphotograph). Price: White Cone E8.90,Black cone/grille £9.50 P&P £1.25.12" 85 watt R.M.S. McKENZIE C1285GP (LEAD GUITAR, KEYBOARD, DISCO) 2"aluminium voice coil, aluminium centre dome, 8 ohm imp., Res. Freq. 45Hz., Freq.Resp. to 6.5KHz., Sens. 98dB. Price: E22.00 + £3 carriage.12" 85 watt R.M.S. McKENZIE m851.c (P.A., DISCO) 2" aluminium voice coil. Twincone. 8 ohm imp., Res. Freq. 45HZ., Freq. Resp. to 14KHz. Price £22 + £3 carriage.15" 150 watt R.M.S. McKENZIE C15 (BASS GUITAR, PA.) 3" aluminium voice coil.Die cast chassis. 8 ohm imp., Res. Freq. 40Hz., Freq. Resp. to 4KHz. Price: £47 + f4carriage.

PIEZO ELECTRIC TWEETERS MOTOROLAJoin the Piezo revolution. The low dynamic mass no voice coil) of aPiezo tweeter produces an improved transient response with a lowerdistortion level than ordinary dynamic tweeters. As a crossover is notrequired these units can be added to existing speaker systems of upto 100 watts (more if 2 put in series). FREE EXPLANATORY LEAFLETSSUPPLIED WITH EACH TWEETER.

TYPE 'A' IKSN2036A) 3- round with protectivewire mesh, ideal for bookshelf and mediumsized Hi-fi speakers. Price £4.29 each.

TYPE 'B' IKSN1005A) 3 super horn. Forgeneral purpose speakers, disco and P.A.systems etc. Price £4.99 each.

TYPE 'C' (KSN5016A) 2" 5" wide dispersionhorn. For quality Hi-fi systems and qualitydiscos etc. Price £5.99 each.TYPE 'D' IKSN1025A)...- 6" wide dispersionhorn. Upper frequency response retainedextending down to mid range 12KHz). Suitablefor high quality Hi-fi systems and qualitydiscos. Price £7.99 each.

TYPE 'E'IKSN1038A) 3 % " horn tweeter withattractive silver finish trim. Suitable for Hi fimonitor systems etc. Price £4.99 each.

TYPE 'F' IKSN1057A) Cased version of type'E'. Free standing satellite tweeter. Perfectadd on tweeter for conventional loudspeakersystems. Price £10.75 each.P&P 20p ea. for SAE for Piezo leaflets).

TYPE 'D'

TYPE 'F'

1K.WATT SLIDE DIMMER Controls loads up to 1KW Compact size

4." 13x 2 1/2"

16

Easy snap in fixing throughpanel/cabinet cut out

Insulated plastic case Full wave control using 8am

triac Conforms to BS800 Suitable for both resistance

and inductive loadsInnumerable applications inindustry, the home, and discostheatres etc.

Price: £11.70 each + 50p PEEP(Any ouantit I

BSR P256 TURNTABLEP256 turntable chassis S shaped tone arm Belt driven Aluminium platter Precision calibrated counter balance Antiskate (bias device) Damped cueing lever 240 volt AC operation IHz1 Cut outtemplate supplied Completely manual arm.This deck has a completely manual arm and isdesigned primarily for disco and studio usewhere all the advantages of a manual arm are

required.Price £ 31 .35 f2 50 P&P

PUWEP AMPLIFIER MODULES

BK ELECTRONICSPrompt Deliveries

VAT inclusive

prices

Audio Equipment

Test Equipment

by

Thandar

and

Leader

KEYBOARDS

011/110f TO10..7..S0V1114.

ZItCP111.. _

MEMBRANE KEYBOARDS ',-manufactured from a tough poly -carbonate film mounted on 1 minglass fibre printed circuit boardassembly incorporating silver platedcontacts.15 way numeric keyboardStandard keyboard providing 0-9and A -F functions.Size: 100mm x 100mm x 2mrn. Price. 115.9e 0 33p p&p

Alpha Numeric Keyboard Full size 55key non encoded keyboard with thecommonly required functions in a

Clwerty array. Matrix output via a 16 pinDIL socket.

Sqe: 350mm x 100mm x 2mm. Price: C13.98 + 50p p&p

100 WATT R.M.S. A t s 300 WATT R.M.S.MODULESPower Amplifier Modules with integral toroidaltransformer power supply, and heat sink. Suppliedas one complete built and tested unit. Can be finedin minutes. An LED Vu meter is available as anoptional extra.

SPECIFICATION:Mae Output Power: 110 watts R.M.S. (OMP 1001

310 watts R.M.S. IOMP 3001Loads: Open and short circuit proof. 4.16 ohms.Frequency Response: 20Hz - 25KHz j3dB.Sensitivity for Max. Output:500mV at 10K IOMP 1001 1V at 10K IOMP 3001T.H.D.: Less than 0.1%Supply: 240V 50Hz

OMP 100 380 x 115 x 72mmOMP 300 480 x 153 x 66rnm

Prices: OMP 100 £31.50 each + f2.00 P&POMP 300 C519.00 each + £3.00 P&P

Vu Meter £5.50 each + 50p P&P

Matching 3 -way loudspeakersand crossoverBuild a quality 60watt RMS system 8ohms

Build a quality 60 watt R.M.S. system.

* 10" Woofer 35Hz-4.5KHz* 3" Tweeter 2.5KHz-19KHz* 5" Mid Range 600Hz-8KHz* 3 -way crossover 6dB/oct 1.3 and 6KHz

Recommended Cab -size 26" x 13" x 13"Fitted with attractive cast aluminium fixing es,cutcheons and mesh protective guilts which areremovable enabling a unique choice of cabinetstyling. Can be mounted directly on to bafflewith or without conventional speaker fabrics.All three units have aluminium centre domesand rolled foam surround. Crossover thinbanes spring loaded loudspeaker terminals andrecessed mountino panelPrice £22.00 per kit + £2.50 postage and pack-ing Available separately. prices on request

12" 80 watt R.M.S. loudspeaker.A superb general purpose twin cone loud-speaker. 50 oz. magnet. 2 aluminiumvoice coil. Rolled surround. Resonant fre-quency 25Hz. Frequency response to13KHz. Sensitivity 95dB. Impedance Bohm.

Attractive blue cone with aluminiumcentre dome.Price E 18.49 each + 12.00 P&P.

B.K. ELECTRONICSVISA

37 Whitehouse Meadows, Eastwood, Leigh -on -Sea, Essex SS9 5TY* SAE for current lists. * Official orders welcome. * All pm

applicable) in special energy absorbing PU foam. Calk,' prior appointment, please phone 0702-527572aT * * All iteols packed (where

7S

100 FREE PROGRAMSFROM SILICA SHOP - WITH EVERY PURCHASE OF AN

ATARI g.88rATARI PRICES REDUCED!

We at Silica Shop are pleased to announce somefantastic reductions in the prices of the Atari 400/800personal computers. We believe that the Atari at itsnew price will become the U.K.'s most popular per-sonal computer and have therefore set up the SilicaAtari Users Club. This club already has a library ofover 500 programs and with your purchase of a 400or 800 computer we will give you the first 100 free ofcharge. There are also over 350 professionally writ-ten games and utility programs, some are listedbelow. Complete the reply coupon and we'll sendyou full details. Alternatively give us a ring on 01-3011111 or 01-309 1111.

ATARI 400 £159with 16K

ATARI 400 £228with 48K

ATARI 800 049Lwith 48K

r400/800 SOFTWARE & PERIPHERALSDon't buy a T.V. game! Buy an Atari 400 personal computer and a game cartridge and that's all you'll need. Later on you can buy the BasicProgramming cartridge (£35) and try your hand at programming using the easy to learn BASIC language. Or if you are interested in businessapplications, you can buy the Atari 800 + Disk Drive + Printer together with a selection of business packages.Silica Shop have put together a full catalogue and price list giving details of all the peripherals as well as the extensive range of softwarethat is nowavailable for the Atari 400/800. The Atari is now one of the best supported personal computers. Send NOW for Silica Shop's catalogue and price listas well as details on our users club.THE FOLLOWING IS JUST A SMALL SELECTION FROM THE RANGE OF ITEMS AVAILABLE:ACCESSORIES Mountain Shoot BUSINESS DYNACOMP Maths-Tac-Toe Scram Castle Sleazy Adventure Jawbreaker PROGRAMMINGCables Rearguard Calculator Alpha Fighter Metric & Prob Solvg States & Capitals Centurion Solitaire Mission Asteroid AIDS from AtariCassettes Star Flite Database Managernt Chornpelo Mugwump Touch Typing Checker King Space Chase Mous kattac k Assembler EditorDiskettes SundarGolf Decision Maker Crystals . Muses. rerms/Notatn Chinese Puzzle Space Trek Threshold Dsernbler (APXIJoysticks Graph -It Forest Fire Musical L -y-i- puler EMI SOFTWARE Codecracker Sultans Palace Ulysses/Golden Fl Microsoft BasicLe Stick - Joystick AUTOMATED Invoicing Intruder Alert My First Alphabet British Heritage Comedy Diskette Tact Trek Wizard & Princess Pascal (APX)Misc Supplies SIMULATIONS Librarian Monarch Number Blast Cribbage/Dominoes Dice Poker Terry Pilot (Consumer/Peddles Crush Crumble Corp Mort & Loan Anal Moonprobe Polycalc Darts Dog Daze Wizards Gold PERIPHERALS Pilot (Educator/

Datestones of Ryn Nominal Ledger Moving Maze Presidents Of U.S. European Scene Jig Domination Wizards Revenge Centronics Printers Programming KitADVENTURE INT Dragons Eye Payroll Nominoes Jigsaw Quiz Master Hickory Dickory Downhill Disk DriveScott Adams Ado Invasion Orion Personal F inl Mgmt Rings of The Emp Starware Humpty Dumpty Eastern Front ENTERTAINMENT Epsom Printers SANTA CRUZNo 1 Adventurelnd Rescue at Rigel Purchase Ledger Space Tilt Stereo 3D Graphics Jumbo Jet Lander Galahad & Holy Grl from ATARI Program Recorder Basics of AnimationNo 2 Pirate Adv Ricochet Sales Ledger Space Trap Three R Math Sys Snooker & Billiards Graphics/Sound . Asteroids RS232 Interface Bobs BusinessNo 3 Mission Imp Star Warrior . Statistics 1 Stud Poker Video Math Flash Submarine Comrndr Jax0 Basketball Thermal Printer Display ListsNo 4 Voodoo Cast Temple of Apshai Stock Control Triple Blockade Wordmaker Super Cubes & Tilt Jukebox Blackjack 16K Memory RAM Graphics MachineNo 5 The Count Upper Reaches Aps Telelink 1 Tournament Pool Lookahead Centipede 32K Memory RAM Kids 1 & 2No 6 Strange Ody Visicalc EDUCATION EDUCATION Memory Match Chess Horizontal ScrollingNo 7 Mystery Fun BOOKS Weekly Planner from APX from ATARI ENTERTAINMENT Midas Touch Entertainment Kit PERSONAL INT Master Memory MapNo 8 Pyramid of D Basic Ref Manual Word Processor Algicalc Cony French from APX Minotaur Missile Command from APX Mini Word ProcessorNo 9 Ghost Town Compute Atari DOS Atlas of Canada Cony German Alien Egg Outlaw/Howitzer Pac Man Adv Music System Page FlippingNo 10 Say Island 1 Compute Bk Atari CRYSTALWARE Cubbyholes Cony Italian Arithill Preschool Games Space Invaders Banner Generator Player Missile GrNo 11 Say Island 2 Compute Magazine Beneath The Pyram Elementary Biology Cony Spanish Attank Pro Bowling Star Raiders Blackjack Tutor Player PianoNo 12 Golden Voy De Re Atari Fantasyland 2041 Frogmaster Energy Czar Avalanche Pushover Super Breakout Going To The Dogs SoundsAngle Worms DOS Utilities List Galactic Quest Hickory Dickory European C & Caps Babel Rabbotz Video Easel Keyboard Organ Vertical ScrollingDeflections DOS2 Manual House Of Usher Inst Comptg Dem Hangman Blackjack Casino Reversi II Morse Code TutorGalactic Empire Misc Atari Books Sands Of Mars Lemonade Inuit To Frog 1/2/3 Block Buster Salmon Run ON LINE SYSTEMS Personal Fitness Prg SILICA CLUBGalactic Trader Op System Listing Waterloo Letterman Kingdom Block 'Em 747 Landing Simul Crossfire Player Piano Over 500 programsLunar Lander Wiley Manual World War III Mapware Music Composer Bumper Pool Seven Card Stud Frogger Sketchpad write for details ..,A

FOR FREE BROCHURES -TEL: 01-301 1111PrF.ori free grochore and reviews on our range or electronic products please telephone GI i301

To oraey by telephone wist Quote your name a...5 credrt card numoer and ord,er requirementsand leave the rest to us Real and pacing 5 FREE OF CHARGE in the UK Express 2a hOordelivery ay... at an additional charge SHOP DEMONSTRATION FACILITIES - we gowde .1/ faculties at our shop in Sidcup Mongav to

Saturday gamto 5 30, IclOging Thursday tOro Friday 80m1AIL ORDER - we are a SpeCialist malt order company 8nd are able 10.0y gags cluec110 your

MOVE n BACK UNDERTAKING -a youarelotally unsatisfied wohyour purcnase you may return it tous witnin 5 days On receipt ol the goods in SaliSMOIOry condon we *P11 give you a kW felony]PART EXCHANGE SECOND HAND MACHINES- we Offer a part excnange Scheme lotrade in manymattes of V games tor personal computersCOMPElli,vE PRICES - our orKes ofiersaroservicea.doevycompelowe Wearenever anowngly

HELPFULand will m match any lower Once quOted by our competitors

NELpFUL ADvICE ova -ale on the Suitabitily of varaus compute,. AFTER SALES SERVICE - ay..° on all computers out of guarantee

SILICA SHOP LIMITEDDept HE 0583 1-4 The Mews, Hatherley Road, Sidcup,Kent DA14 4DX Telephone 01-301 1111 or 01-3091111

11111

111lu111110

111110 911M

r FREE LITERATURE 1I am interested M purchasing an Atari 400/800 computer and wouldlike to receive copies of your brochure and test reports as well asyour price list covering all of the available Hardware and Software.

Name

Address

Postcode

HE 5_82A

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lectronics For - WorldRadioHistory.Com...*CAREERS IN ELECTRONICS PART 1 12 The first in a major new series. FAMOUS NAMES 24 Charles Proteus Steinmetz. RADIO RULES 41 Concluding with