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PREFACE v28
1
Beam-Direction Marker Circuit for Scope
Gives Comet-Shaped Trace. Magnetically Deflected Oscilloscope Uses 21-
Inch Television Picture Tube. 281
31
2 31
3 32
4 35
6 35
7
ALARM CIRCUITS. Balanced-Capacitance Antenna Alarm Pro-
tects Barbed-Wire Fence. Comparator Circuit for Magnetic-Tape
Printer Sounds Alarm If Copy Deviates
from Master. Failure of Picture or Sound Carrier Trips TV
Transmitter Alarm Conelrad Alarm Is Triggered by Loss of Re-
ceiver A VC Voltage Crystal Transducers in Acoustic Chamber
Detect Breaks in Moving Film. Electronic Highway Scale Trips Alarm If
Moving Truck Is Overweight. Transistorized Crevasse Detector Uses A-F
Transmitters and Receivers.
368
3810
3910
12 40
13 43
14 44
15 44
18
4518
2047
20 49
21 51
QOMPUTER CONTROL CIRCUITS. ..
Transistorized Gate, Flip-Flop, Counter and
Shaper Circuits for Digital Computers. .
Read and Write Amplifier for Digital Data in
Tape Systems Dual Chopper-Stabilized Operational Ampli-
fier for Analog Computers. Simple Operational D-C Amplifier Is Basis of
Desk-Size Differential Analyzer. ...
Analog-Digital Converter Generates Pulse
Frequency Proportional to D-C Input Volt-
age. Direct-Coupled, Emitter-Coupled and Resis-
tance-Coupled High-Speed Flip-Flops ..
Transistorized Trigonometric Function Gen-
erator Provides Cosine of Input Voltage .
Precision Digital Delay Generator for Radar
and Sonar Calibration and Target simu-
lation Sine-Cosine Approximator for Radar Com-
puter Uses Diode Function Generator. .
Nine-Bit Word Generator Ghecks Digital
Computers at Pulse Rates up to 1 MC ..
Probability Computer Produces Output Pulse
When Noise Exceeds Reference Threshold .
Digital Comput~r Clock Circuits Use Ger-
manium Transistors Either at Saturation
orCutoff Triangular-Wave Generator and D-C Opera-
tional Amplifier Serve in Analog Multi-
plier Transistor Matrix Gives Simultaneous Binary
Addition and Multiplication. Combined D-C Amplifier and Chopper Am-
plifier Give High Zero Stability. Zero-Crossing Detector Aids Analysis of
Brain Waveforms. Transistorized Analog-Digital Converter Uses
Feedback Subtraction.
22 51
23 53
5724
AUDIO CONTROL CIRCUITS" .." "
Speech Rejector Differentiates between
Damped Speech and Undamped Music. .
Biased-Diode Squelch Circuit Mutes Mag-
netic-Tape Print-Through ." " .."
Speech-Music Discriminator Silences Radio
Loudspeaker During Commercials" " "
Automatic Speech Amplitude Control Pro-
vides Differentiation and Clipping" ". .
Automatic Fine Tuning Circuit Controls TV
Sound-to-Picture Ratio. " Heartbeats Are Made Audible by Frequency~
Modulating 1,OOO-CPS Oscillator" " " .
Burst-Modulated A-F Transmitter Controls
Tuned-Reed Induction Paging Receivers .
CATHODE-RAY CONTROL CIRCUITS" .
Ferrite Disk on Engine Shaft Generates Input
for Cathode-Ray Retation Analyzer " " .
Four- Thyratron Sawtooth Pulser PI:oduces
True Voltage-Curreht Curves on Scope. "
Electronic Shutter forf{V Kinescope Recorder
Passes Exactly 525 Lines. " .
Isoecho Contour in ~eather Radar Shows
Center of Thunderstorm. " Signal- Triggered Sweep Magnifies Pulse
Widths on Scope" ..." "
Synchronizer Feeds Transients to 12 Cathode-
Ray Tubes Having Different Base Lines .
~
26 57
COUNTING CIRCUITS. Transistorized Decade Counter Uses Cas-
caded Bistable Multivibrators
VII
CONTENTS
8857
59 8991
6001
6293
6495
6796
6796
6997
72 98
Batching Counter Actuates Solenoid at Prede-
termined Count and Resets Automatically.
Unijunction Transistors Simplify Design of
Bistable Stages for Ring Counter. ...
Reversible Binary Counter Determines Vari-
ations in PCM Pulse Intervals. ...~
Coincidence Detector Counts Missing Pulses
in Radar Magnetron Output. Automatic Bacteria Colony Counter Uses
Anticoincidence Circuits. Loudspeaker Serves ItS Microphone for Sim-
ple Shot and Blast Counter. Predetermined Counter and Gate Fire Flash-
lamps in Missile Test Lab. Four-Decade Decimal Counter Uses Beam-
Switching Tubes. Ring-of-l0 Counter Having Four ON Stages
Requires Only Three Feedback Resistors
PerStage Binary-Decimal Counter Uses Logical AND
Gates in Feedback Loop. 74 99
Level-Deviation Detector Locates Flaws in
Magnetic Tape. Recorded Tone Bursts Permit Dialing of 45
Taped Spot Announcements Automatic Stop Circuit for Tape Recorder .
Electrode Drive-Motor Servo for Spark Ma-
chining Auto Transmission Gear Contour Gage Con-
trols Automatic Bobber and Gear Sorter .
Four-Transistor Inverter Drives Two-Phase
Drag-Cup Servo Motor. Muscle Potentials of Patients Control Respi-
ration Rate of Iron Lung. Tracer Control Circuit Maintains Constant
Cutting Velocity for Milling Machine. .
Three-Feed Control System for Metal-Cut-
ting Band-Saw Carbon Dioxide Analyzer in Feedback Loop
Controls Valve Motor. Ei~ht Audio Tones Recorded on Magnetic
Tape Control Overhead Crane. Circuit Controls Vacuum Actuators of Bigh-
Speed Tape Transport.
76
MAGNETIC AMPLIFIER CIRCUITS76
76
78
79
81108
82100
83110
84112
84113
Transistor Magnetic Inverter Uses Differen-
iial Multivibrator for Signal or Power Con-
version. Magnetic-Amplifier Square-Law Circuits
Serve in Four-Quadrant Analog Multiplier .
Magnetic Amplifiers and Saturating Trans-
former Regulate D-C Power Supply. ..
Self-Balancing Magnetic Amplifier Drives
400-CPS Servo-Motor. Magnetic Servo Amplifier Drives Gyro Indi-
cator Magnetic Amplifiers Control Frequency and
Voltage of Reflex Klystron. Magnetic-Core Frequency Divider Controls
ITV Sync Generators. Half-Wave Magnetic Amplifier Drives Two-
Speed High-Impedance Servo-Motor. ..
Saturable-Core Transistor Oscillator Inte-
grates Gas Flow Data. Synchronously Switched Biased Diodes In-
crease Gain of Magnetic Amplifier. ..86
114
86MEt\SURING CIRCUITS 116
DIRECT-CURRENT AMPLIFIER
CIRCUITS , , , , , , , , , , ,
Feedback Increases Input Impedance ofTransistor D-C Amplifier " , , , , ,
D-C Amplifier for Voltmeters and Analog
Computers Has Infinite Input Impedance
and Infinite Voltage Range, , , , , ,
Wide-Band .Differential Amplifier for Null
Detection""",..",
Silicon-Diode Electronic Chopper Stabilizes
All-Triode D-C Amplifier, , , , , ,
Low-Drift Transistorized Differential D-C
Amplifier Uses Silicon Temperature-Com-
pensating Resistor, , , , , , ...
Junction- Transistor D-C Amplifier for Tran-
sistor Voltmeter , , ...
Differential Input Stage Improves Feedback
Stabilization of D-C Amplifier, Vibrating-Capacitor Modulator Changes D-C
Output of Differential Analyzer to A-C , .
Electronically .'ontrolled Chopper Boosts
Sensitivity of Infrared Detector. ., .
Twin- Triode Electronic Chopper Handles
High D-C I~ut Voltages, *
Feedback Throiigh Pentode Holds Cathode
Follower at Unity Gain. .., , ..
~lmp\~ Dl~~T~ntla\ D-C A.mp\\n~T l()T C()ntT()\
Systems Amplifies Difference Between Two
Signals, ..., ..., ., , . 87
1168~MACHINE CONTROL CIRCUITS. ...
Size Control Circuit for Automat~c Cylinder
Hone. ~ 117
D-C Error Voltage of Resistor-Checking
Wheatstone Bridge Is Amplified to Drive
Go-No-Go Meter. Circuit Delivers Pulse Width Proportional to
Time That Signal Is Between Specified
Voltage Levels.
...
CONTENTS
lfiO
llR
150
119JfiO
1201.~2
121153
METAL DETECTOR.CIRcUITS Proximity Control Responds to Any Metal
Near Pickup Coil. Magnetic Concentricity Gage Trips Flashtube
Trigger Circuit. Detector Traces Buried Cables Carrying 250-
CPS Signal. Tack Detector for Shoes Trips Alarm When
Probe Touches Metal. Inexpensive Metal Detector Locates Con-
cealed Conduits. Pipes and Ducts. ...122
154
1231.116
12.1'j
156125
1!>6
1261.~~
127 159
160127
,
MULTIVIBRATOR CIRCUITS. Two Multivibrators and Variable Delay Line
Generate Variable-Width Pulses. ...
A-C Tachometer Drives Multivibrator Cir-
cuits of Expanded-Scale Speed Indicator .
Multivibrator, Blocking Oscillator and
Counter Circuits Simulate Radar Targets .
Fast-Switching Multivibrator-Controlled Re-
lay Circuit Electronic Chopper Replaces Vibrator in
Television Modulation Indicator. ...
Simple Sweep Generator for Oscilloscopes Has
Range up to 500 KC. 11'\1
129
163129
130 163
131
163134
165
13.1) 167
137 lfi7
138
168140
169141
,
NUCLEONIC CIRCUITS. Transistorized Geiger-Muller Probe Traces
Radioisotopes in Oil Well. Time Interval Analyzer Uses Modified
Chronotron Circuits to Time Nuclear Par-
ticle Flights Transistorized Geiger Counter Has High-
Voltage Generator and Ratemeter ...
Cold-Cathode Count-Rate Circuits Monitor
Alpha Radiation. Eddy-Current Circuit Detects Hairline Flaws
inFineWire Time-of-Arrival Indicator Blows Fuse to
Stop Clock When Radioactive Fallout Ar-
rives. Transistorized Gamma-Radiation Monitor
Uses D-C/D-C Converter. Simple O-M Radiation Monitor and Re-
corder. .. 171142
172143
144
14,1)
Pulsed Eddy Currents Measure Thickness of
Metal Coating on Base Metal. Phase Comparator Locates Null as Float
Moves Core of Differential Transformer in
Liquid D.ensity Gage. Magnetic Quadrupole Is Probe of Magne-
tometer Using Servo Loop. Fast-Acting Nonlinear Feedback Stabilizes
Gain of Transistorized Pulse Amplifier. .
Ergmeter Uses Bolometer Bridge to Measure
Energy of Discharging Capacitor. ...
Automatic Range-Selecting Servo for Elec-
tronic Voltmeter Electronic Integrator-Amplifier Speeds Grad-
ing and Matching of Magnetic Cores. ..
Hot-Wire Thermal Bridge Is Voltage Stand-
ard for Expanded-Scale A-C Voltmeter. .
Bootstrapped-Collector Circuit for Starved
Transistor Has 500-Megohm Input Resist-
ance Differentiating Circuit Accurately Locates
Zero of A-C Voltage. Counter on Shaft of Servo-Driven Self-Bal-
ancing Potentiometer Gives Digital Pres-
entation for VTVM Tuned Voltmeter Measures First Four Har-
monics of Power-Line Frequency. ...
Meacham-Bridge Oscillator and Frequency
Detector Measure Ice Coating Thickness .
Admittance-Measuring Circuit Determines
Setting Time of Cement. Linear Potentiometer and Operational Am-
plifier Serve as Wide-Range Tachometer .
Capacitance Pickup on Angle-of-Attack Po-
tentiometer Boosts Accuracy. Schering Bridge and Phase-Sensitive Volt-
meters Sort Capacitors in Tolerance
Ranges. Portable Vibration Meter Uses Transistorized
Integrating Amplifier and Demodulator .
Automatic Waveform Detector Uses Time-
Sampling to Sort Ferrite Cores. Thickness of Nonferrous Metals Is Gaged
by Electromagnetic Absorption. Flutter and Wow Mete:t Measures Variations
in Tape Recorder Transport Speed. ..
Checking Insulation R$Sistance of Pressure-
Sensing Potentiometvs Second-Harmonic Flu~Gate Magnetometer
Serves as Steel Tubing Hardness Tester. .
Tester Checks Static and Dynamic Unbalance
of Dual-Triode Sections. Dual-Channel Doppler Radar Serves as Rate-
of-Climb Meter. Automatic Go-No-Go Comparator Makes 350
Checkout Measurements on Missile ---
OSCILLATOR CIRCUITS. Self-Quenching Superregenerative Oscillator
Produces Pulses of 500-CPS Tone. ...
Pulse Genetator Feeds Controlled-Duration
Signals to Two Channels. Pulse Modulator Gener~tes Uniform Pulses
for Widely Varying Load.147
ix
CONTENTS
175 200
176 202
204177
178 204
179 205
180 207
1 Rl 207
181
208
182
20~184
18., 210
186 212
187 212
188
2141~~
21.1)189
Frequency-Modulated Light Beam Completes
Feedback Loop for Control System. ..
Stabilized Photoformer Circuit Feeds Func-
tion of Input Voltage to Analog Computer .
POWER SUPPL y CONTROL CIRCUITS .
Overcurrent Protection Circuit for Transistor
PowerSupply. Energy in Received Radio Waves Provides
Operating Power for Transistor Circuits .
Junction Transistor Serves as Ripple Filter
for Low- Voltage Power Supply. Control of Instantaneous Voltage and Current
in Power Transistor Boosts Efficiency. .
Servo Discriminator Feeding Silicon-Diode
Modulator Controls Aircraft Alternator
Frequency' Crystal-Controlled 28- Volt Bistable Voltage-
Doubling Chopper Drives Synchronous
Clock. Photoflash Power Conyerters Use Power
Transistors in Symmetrical Inverter and
Blocking Oscillator Circuits. Zener Diodes and SilIcon Transistor Regu-
late Output of Bridge Rectifier. Controlled-Firing- Time Thyratron Inverter
Eliminates Bulky Saturable Reactors. .
Solid-State Rectifiers and High-Current Reg-
ulator Tubes Eliminate Power Transformer
in Regulated Power Supplies. R-F Power Supply Replaces Vibrator Supply
for Portable Infrared Viewers. Regulated Transistor Power Supply Uses Di-
rect-Coupled Amplifier in Feedback Loop .
Transistorized Power and Bridge Excitation
Supply for Strain-Gage System. ...
High-Voltage Power Supply Uses 12.5-KC
Oscillator and Corona-Tube Regulator. .
Variable-Frequency Power Supply for Servo
Testing Uses Pentode Cathode Followers .
Triode Serves as Grid Leak Resistor in. Regu-
lated Power Supply.
Beat-Frequency Subaudio Oscillator Requires
No Output Amplifier. Electronic Organ Uses Neon Lamps as Tone
Generators and Frequency Dividers. ..
Closed-Loop Regulator Controls High-Power
Induction Heater. Direct-Coupled Multiple-Feedback R-C Os-
cillator Covers 4 CPS to 350 KC. ...
Variable-Frequency Oscillator Controls Fir-
ing Rate of Machine Guns. Double- Triode and Two Diodes Generate
Negative-Going Staircase. Oscillator Provides Beeps Required when Re-
cording Telephone Conversations. ...
Thyratron Delivers Predictable Half-Sine
Pulse When Triggered. Fork-Controlled Generator Provides Seven
Standard Audio Frequencies Simultane-
ously : ...
Oscillator-Sharing Simplifies Circuit of Elec-
tronicOrgan Neon Tubes Back to Back Generate Keep-
Alive Pulses for Recorder. Low-Distortion Audio Oscillator Uses Biased
Diodes to Eliminate Hunting. Transistorized Crystal-Controlled I-MC Os-
cillator Is Highly Stable. Sonar Target Simulator Produces Echo Sig-
nal for Servicing Purposes. Variable-Gain Negative-Feedback Amplifier
Stabilizes Feedback Oscillator. Frequency Meter Quickly Measures Dynamic
Compliance of Phono Cartridge. ...
Frequency Comparator Applies Error Voltage
to Repeller of Klystron Oscillator. ...
216189
216
PHOTOELECTRIC CIRCUITS 191
218
191 219
192 220
222]9~
195 222
195 224
19fi 225
198 226
198 227
Camera Shutter Tester Uses Photodiode to
Feed D-C Amplifier. Multiplier Phototube on Lathe Drives Elec-
tronic Counter That Reads Microinches ..
Photoelectric Function Generator Uses Oscil-
loscope as Light Source. Photoelectric Ill~ination Control Responds
to Bright Sunlight. Vidicon Camera Circuits Detect Changes in
Nearly Identic It Photographs. Banks of MultiplIer Phototubes Give Coor-
dinates of Test Missile. Photocell-Controlled Multivibrator Gener-
ates Tone Frequency Proportional to Light .
Photoelectric Counter Checks Frame Rate of
MovieCamera Three-Phototube Pickup Checks Hue and
Saturation of Color TV Tubes.
PROCESS CONTROL CIRCUITS. ...
Basic Amplifier, Modulator, Demodulator and
Power Supply Circuits for Process Control.
Audio-Level Trigger Circuit Shuts,Off Crys-
tal Lapping Machine. Closed-Loop Controller Provides Rate and
ResetAction Three-Channel Decade Counter Controls
Flow of Liquid Plastics. ~Pressure Transmitter Controls Tuned Oscil-
lator for Set-Point Control. Galvilnometer-Type Controller Feeds F-M
Circuit Giving D-C Output.199 227
x
CONTENTS
Servo-Controlled Pump Maintains Constant
Fluid Volume. 228
REMOTE CONTROL CIRCUITS 230
230
230
232
233264
234
235
236
237
240
Transmitter and Receiver Circuits for Radio-
Controlled Garage-Door Opener. ...
Single-Stage Franklin Superregenerator for
Radio Remote Control. Ultrasonic Gong Controls Four Functions in
TV Set. Carrier-Current.Control Through Power Line
Tunes TV Set. Microwave Link Controls Fog Alarm on un-
attended Island Site. Selective A-F Circuit Fires Squib or Operates
Relay for Missile Control. Ultrasonic Tones Control Tuning Motor in
TV Set. Tone-Actl1ated Programmer Mixes Records
with Taped Announcements. Two-Transistor Superregenerative Remote
Control Receiver. Flashlight Operates Photoelectric Remote
Control for TV Set. 241
SERVOMECHANISM CIRCUITR 242
242
SWITCHING CIRCUITS Simple Electronic Switch Gives Transient-
Free Commutating Zener Diode Controls Triggering Level of
Push-Pull Transistor Relay. Ring-of-Five Neon-Lamp Oscillator Pro-
vides Sequential Switching. Clearing, Resetting and Transfer-Storage
Circuits for Beam-Switching Tubes. ..
D-C Voltage Comparator Actuates High-
Speed Transistorized Electronic Switch. .
Balanced -Input Transistorized Electronic
Relay. Two-Way Sampling Switch Using compen-
sated Comparators Has High Input Impe-
dance. Beam-Switching Tube Switches Low-Level
Capacitive Transducer Signals. Voice-Actuated Switching Circuit Controls
Microwave Party Li~e ' .
Triode Makes Relay Pull-In and Drop-Out
Currents Equal. Multichannel Electronic Switch for Oscillo-
scope Uses Flip-Flops in Ring. Electronic Crowbar Shorts Power Supply of
High-Power Transmitting Tube to Prevent
Flash-Arc Damage. Coincidence Diodes Gate Transistorized Six-
Channel Electronic Switch. Saturated and Nonsaturated TransistOJ; Flip-
Flops Use Single and Double Triggering .
Ultrasonic Switch Controls Diversity Re-
ceivers
274242
27.~243
276244
24.1j 276
246 276
247 27R
248 280
250281
251 283
251 284
252 288
Servo Amplifiers Use Power Transistors to
Drive A-C or D-C Motors. .: ...
Silicon Power Transistors Drive Split Control
Winding or Servo-Motor. Zener Diode in Feedback Loop Provides AGC
forA-CServo Servo Accelerometer Uses R-F Oscillator with
NuIIBalance Servo Positioner for Component Inserter Is
Programmed by Cards or Tape. Self-Setting Servo Gate Rejects Random In-
terference Pulses. Negative Feedback Provides Stability for
Push-Pull Transistor Servo Amplifier. .
Servo System Controlled by Radar I-F Signal
Tunes Magnetron for Search or AFC ...
Phase-Seleciive Gate Ilejects Quadrature Sig-
nals in Servo Loop. Transistorized Relay ~ervo Uses Step-Func-
ti on Potentiometer. Transistorized Servo Amplifier Drives Two-
Speed Motor Directly. Four- Transistor Preamp-lifier Feeds Tran-
sistor-Magnetic Amplifier Servo. ...
Simple Infrared Analyzer Detects Leaks in
Air Chamber. Phase-Stabilized UHF Servo Amplifier Con-
trols Steerable Antenna.
253 289
TELEMETERING CONTROL CIRCUITS ,
Transistorized Micromicroammeter FeedsRadiation Data to Satellite Telemeter. ,
Underwater Telemetering System Uses Four60-KC Ultrasonic Links, , ..., ,
Pulse-Position Telemetry Demodulator Com-pensates for Parameter Variations , .,
Transistorized Telemeter Transmitter forBalloon-Borne Radiation Detection. , .
Transistorized PDM Keyer Improves Air-borne Telemetering System, , , , , .
Telemetering Equipment in Sounding BalloonMonitors Cosmic Radiation. , , , , ,
Encoded Shaft P~ition Data Is Transmittedover Telephone Line, , , , , , " ,
Telemetering Transmitter in Rocket ProducesPWM F-M Signals. .., , ., .,
Eight-Transistor Transmitter TelemetersScalp Voltages. , , ., , , ., ,
Telemetering Demodulator Converts Wide-Band F-M Data to PFM Data .256 289
XI
CONTENTS
292 307
292 307
29~ 307
30829Fi
TEMPERATURE CONTROL CIRCUITS
Proportional Heat Control Maintains Ther-
mal Chamber at Preset Value Thennopile Actuates Current-Adjusting
Temperature Controller. Servo-Balanced Bridge for Compensated
Thermocouple Gives Jet Engine Tempera-
ture Germanium Transistor Serves as Thennostat
for (;old .Tlmct.inn -
309297
310298
31229~
312298
~14299
314~Ol
316
~O2 ~1.7
319~o~
321
304321
304 322
TIMING CIRCUITS. Extending Linearity Range of Thyratron In-
tervalTimer Phantastron Circuit and Miller Integrator
Used in Exposure Timer. Millisecond Timer and Thyratrons Stop Die-
Cutting Press after Cut- Through. ...
Doppler Radar Speed Meter Checks Highway
Traffic. Regenerative Frequency Dividers for I-MC
Crystal Source Provide l-KC Power for
Precision Clock. Four-Thyratron Timer Triggered by Vertical
Drive Pulses Exposes Camera for One TV
Frame. Double- Triggering Improves Stability of
Phantastron Frequency Divider. ...
Current Transformer and Electronic Relay
Turn on Running- Time Meter When Any
Power Tool Is Used. Ticks of Master Clock Synchronize Time
Base of Cathode-Ray Watch Timer. ..
Astable Multivibrator Controls Pentode Gate
for Pulsing Circuit.
305 323
ULTRASONIC CIRCUITS. Doppler-Effect Ultrasonic Burglar and Fire
Alarm Battery-Operated Resonance-Type Ultra-
sonic Thickness Gage. Ultrasonic Vibrator Makes Beer Foam to
DriveOutAir. Adjustable Ultrasonic Paths in Air Simulate
Multipath Communications. Ultrasonic Pulses Detect Flaws in Coating of
Uranium Slug. Two-Transistor Broadband Ultrasonic Pre-
amplifier for Hydrophones. Pulsed Frequency-Modulated System Ana-
lyzes Ultrasonic Signal Returns. ...
Piezoelectric Transducer Drives Tip of Ultra-
sonic Soldering Iron. Ultrasonic Phase Meter Measures Subsurface
Water Velocity. Quartz-in- Water Delay Line Simulates Radar
Moving Targets. Two-Receiver Ultrasonic System Measures
Propagation in Sea Water. Driver for Magnetostriction Transducer of
Ultrasonic Impact Grinder. WELDING CONTROL CIRCUITS. ...
Capacitor-Discharge Spotwelder Control
Handles Metal Foils. Timer Controls Thyratrons in High-Speed
Resistance Welder Five-Function Programming Timer Con-
trols Electrode Welder. Toroid Feeding A-C Electronic Voltmeter
Measures Spot-Welding Current. ...~O6 325
.
."
xii