Indian Telephone Industry Raebareli

Vocational Training

Report

In

ITI Ltd. Raebareli

Prepared by: Prateek Srivastava Electronics & Communication

Final Year (4th year) Feroze Gandhi Institute of Engineering & Technology

INTRODUCTION This Report on Vocational Training of the undersigned is based on the actual observations, information’s obtained, study/ actual work done by the undersigned regarding facilities available/ activities being performed in ITI Limited, Raebareli. (PRATEEK SRIVASTAVA)

Preface For effective learning of technical knowledge & concepts, theory and practical make a vicious circle i.e. each strengthen the other. While vocational trainings undertaken at times while doing an engineering Graduation help a lot in further undertaking the theoretical concepts taught in the class room, the theoretical concepts help a lot in having a deeper appreciation of industrial activities and various alternatives of solving a problem. Keeping the above in view the undersigned underwent a vocational training programmed from 11-06-2008 to 07-07-2008 at Rae Barely unit of M/S ITI Limited, the first Public Sector Undertaking of free India, established in 1948 with corporate office at Bangalore and having manufacturing plants at Bangalore complex, Naini (Allahabad), Rae Barely, Shrinagar, Mankapur (Gonda), Palakhad, Electronic City Unit (ECU) at Bangalore. The efforts have been done to understand the basics of working of various departments/ systems of Raebareli unit of this telecommunication company while laying special emphasis on their Tool design and Tool Room Departments. The undersigned also designed two press Tools (one for piercing operation and another for Blanking operation), one injection Maudling Tool and Jigs & Fixtures. The undersigned also observed/ studied the manufacturing of tools in their Tool Room Shops on the convectional as well as some Special Purpose Machines (SPM). The undersigned is confident that this vocational training will definitely help in furtherance of theoretical knowledge and technical concepts during onward course curriculum. (PRATEEK SRIVASTAVA)

ACKNOWLEDGEMENT Firstly, I would like to place on record my thankfulness to Management of ITI Limited and their Human Resource Development Department for giving me an opportunity to do my vocational training in ITI Ltd., Raebareli. It has been a wonderful experience to visit public sector unit totally dedicated to the manufacturing of telecom equipments. I have received immense help and co-operation during my vocational training from DGM(ITI),HRD I express my deep sense of gratitude to all the above gentlemen who helped me to learn a lot of things in practical aspects of industrial activities. I am also thankful to the other staff members.

By: Prateek Srivastava ELECTRONIC & COMMUNICATION FEROZE GANDHI INSTUTE OF ENGINEERING & TECHNOLOGY

RAEBARELI

CONTENTS

Sl. No. Name Of The Chapter Page No.1

2

3

4

5

6

Brief Company Profile

Electronics Switching Line-1

Electronics Switching Line-2

Surface Mount Technology

GSM Technology

Wave Soldering

6 8 16 18 23 34

INTRODUTION OF COMPANY It is the objective of every country either developed or developing to productivity of important product by providing different kind of facilities in order to improve the national income & to complete market. It limited first public sector undertaking being setup after independence it was established in 1948 as a dept. undertaking which was converted into limited company in 1950. The foundation stone of ITI RBL was laid by the Prime Minister Miss Indira Gandhi in October 1973 for to manufacturing of step by step exchange equipment at RBL. ITI Ltd has following unit ITI Ltd Raebareli ITI Ltd Manikapur ITI Ltd Banglore ITI Ltd Naini ITI Ltd Palghat ITI Ltd Srinager

1. Brief company profile

M/S ITI Ltd. Rae Barely is an ISO 9001:2000 accredited public Sector

Undertaking established in the year 1974 with Registered and Corporate

Office located at Bangalore. From a small beginning it has grown into a

mammoth Multi Division Enterprise with state of the art manufacturing

plant located at Doorbhash Nagar, in Raebareli City which is well

connected by train, road as well as by air from Lucknow and is one &

half hour drive from Lucknow. The Company is dealing with diverse

technologies continuously phasing out old technologies and phasing in

new technologies, the Company has Technology/ alliance with the

reputed Telecommunication giants/ leaders as given below:

Prominent among collaborators are ASCOM Switzerland for Switching

Mode Power Supply system. Lucent technologies for GSM Mobile

Communication Systems and Wireless on Local Loop. Westech Korea for

FWT WLL CDMA System the Centre for Development of Tele-Metrics

(C-DOT) has provided indigenous technologies for Rural Automatic

Exchanges (RAX) and Main Automatic Exchanges of medium and large

capacities. ITI BG has provided technologies for HDSL & DPG products.

ITI Raebareli Plant is planning to have non DOT/ BSNL orders such as

Defense, Railways, and Power Sectors. In IT Sector also Raebareli plant

has plants in software development and other allied works. ITI

Raebareli’s contribution to National Telecommunication Net work is up

to 3.1 million lines. ITI Limited Raebareli is ISO 9001:2000 Quality

System Certified Company from Kema Quality B.V.Netherland.

The ITI Raebareli has broadly been divided into two sub divisions’ i.e.

i) ESL -I (ELECTRONIC SWITCHING LINE - 1)

ii) ESL -II (ELECTRONIC SWITCHING LINE - 2)

THE PRODUCTS OF THE COMPANY

• ESL -1 DIVISION

a) SMPS Power Plant system

b) HDSL - types-1 to 4 (HDSL LINE DRIVER (2PAIR)

c) INSTALATION WORK OF GSM

d) CorDECT WLL

PHASED OUT PRODUCT

e) TDMA PMP System

f) Digital Pair Gain (0+4)”CABLE SEVER”

• ESL -II DIVISION

a) C-DOT DIGITAL SWITCHING SYSTEM

b) FWT + MOBILE

c) GSM

2.

ESL-I (Electronics Switching Line) The ESL-I department can be broadly divided into two main parts namely: - 1. SMPS (Switched Mode Power Supply) 2. CorDECT-WLL

SMPS PROJECT

SWITCHED MODE POWER SUPPLY (SMPS)

The power system is intended primarily to provide uninterrupted

DC power to Telecom Exchange and current for charging the batteries.

The system works from commercial AC mains which is rectified and

regulated to -54V DC and is fed to the equipment (exchange). The system

has provision to connect a maximum of three sets of VRLA (valve

regulated lead acid) batteries and facility to charge them simultaneously

to ensure that uninterrupted DC power is always available to the

exchange.

SMPS is a power supply, which is used for supplying power to the exchanges. In ESL-I, SMPS project is divided into two main parts: - (I). Production (II). Testing The production part of the SMPS comprises with the assembling of the components on the Printed Circuit Board (PCB) of the cards needed in the manufacturing of the SMPS. Components are first kitted and then inserted on the PCB. This is called first insertion. Then these are soldered using wave soldering. Sometimes there may be shortage of some components. In that case, instead of waiting for the supply of those components, the PCB is sent for wave soldering. Then on arrival of the required components, the PCB is sent for second insertion, in which soldering is done manually.

Main Store Kit store

Component Card Forming Preparation

First Insertion Stage Quality Control

Wave Soldering

Second Insertion Testing Card Packing

Testing Section involves card testing and then module testing. This is

essential for the correct functioning of the SMPS. Testing is done in

several stages, manually, electronically and software based. The modules

are also tested against any adverse conditions of very hot atmosphere in

the BURN IN Room where the SMPS system is tested at the temperature

of 55-degree Celsius and above, for 72 hours. They are tested at the

maximum value of their output. These all tests are done to maintain the

quality of the SMPS.

The power system -48V, 600A has the following features:

• Multirack configuration having one main and two extension

racks.

• Facility to parallel a maximum of 6 nos. of 100A (5600W)

rectifier modules operating from three phase 400V (phase to

phase) 50Hz AC.

• Termination for three sets of VRLA batteries and exchange.

• System input: Three phase, four wire and 50Hz supply. The

power system has a single bus called auto float/charge bus.

Depending upon the status of the batteries, the output DC voltage

is maintained at 54.0 V with tolerance of 0.5V under auto float condition.

During auto charge the maximum DC voltage reached across the bus is -

55.2V.The exchange, battery and rectifier modules are connected in

parallel.

The system employs natural convection cooling and has AC input distribution, DC output distribution, protection and alarm circuitry for rectifier, battery and equipment.

FUNCTIONAL DESCRIPTION OF POWER SYSTEM

The 48V/600A-power system consists of the following multi-rack

configuration:

• One main and two extension racks.

• AC distribution arrangement in each rack.

• Rectifier modules (6 nos. max.).

• DC distribution arrangement in main rack.

• Power system controller card in main rack.

• Display and alarm card in main rack.

• TEMCO (temperature compensation) card in main rack.

TECHNICAL SPECIFICATION

FOR MODULE:

1. Input voltage:

• 320V to 480V rms three phase(nominal voltage: 400V)

• Frequency: 45Hz - 65Hz

2. Output voltage:

Float mode:

• nominal voltage: -54.0V with tolerance 0.5V

• adjustment range: -48.0V to -56.0V

Charge mode: -55.2V (max)

3. Rated current: 100A

4. Psophmetric noise: Less than 4mV without battery floated.

Less than 2mV with battery floated.

5. Input power factor: Greater than 0.98 with 50% to 100% load

at nominal input.

6. Efficiency: Greater than 90% at full load and nominal input.

7. Protection:

• Short circuit protection.

• Input over/under voltage protection.

• Output over voltage protection.

• Constant current features settable from 50A to 100A in auto

float/charge mode.

Alarms and indicating lamps:

• auto float/charge : green LED

• over voltage: red LED

• alarm (DC output fail/under voltage): red LED

• over-load (voltage drop):amber/yellow LED

• mains ok : green LED

CARDS USED IN SMPS

The various types of cards used in the SMPS are follows: - • IFC 52

• Mastin

• Secin 1(1400W)

• Secin 3(5600W)

• Primin 1(1400W)

• Primin 3(5600W)

• PSC card(power supply controller card)

• Display and Alarm card

• TEMCO card

SMPS MODULE

INTRODUCTION: The SMPS 48V-5600W is a three phase, unity

power factor power supply with a wide input voltage range of 3 x

185Vac to 275Vac (with neutral wire) and with a useful output power of

5600 W delivered to the load. This unit has been developed for cost

effective but highly intelligent modular telecommunication power

system.

Primary application of the rectifiers SMPS 48V-5600W are in the supply

of Telecom Equipment, where it can provide temperature dependent

charging of back-up batteries without using power system controllers.

The connection-cooled unit may be operated up to 60-degree Celsius

ambient air temperature. The rectifier operates from a nominal 3*230Vac

rms (with neutral wire) source. The main frequency may vary from 45Hz

to 65Hz. Total harmonic distortion (THD) of the input current

waveform is below 5%. The output of the rectifier conforms to the

generic requirements of telecommunication power supplies in terms of

noise, voltage programmable as well as over voltage.

Two modes in which SMPS works are:

1. Auto Float

2. Auto Charge

TYPES OF SMPS MODULES

1.48V/1400W/25A SMPS:

Single-phase unity power factor supply with a very wide input voltage

range of 150Vac to 275Vac and with a useful output power of 1400W

delivered to the load. This unit has been developed for cost effective but

highly intelligent module telecommunication power system.

2.48V/5600W/100A SMPS:

Three phase unity power factor. Power supply with a wide input voltage

range of 3 x 185Vac to 275Vac and with useful output power supply of

5600W delivered to the load. Work of both SMPS is same-SMPS

48V/1400W is used where, we need lower power supply like that in rural

areas and SMPS 48V/5600W are used where we need wide range of

power supply to exchange.

ADVANTAGES • best regulation

• feed back

• best efficiency

• best controlling

• usable at high frequency

• over temperature and over load protection

GENERAL DESCRIPTION OF OPERATION

The SMPS 48V-5600W rectifier is a state-of-the-art switch-mode power

supply. It is composed of three identical single-phase sub-modules (R, S

and T) as shown in the block diagram.

The sub-modules are connected between neutral and one of the phases (R,

S and T) on the input, and in parallel on the output. All '-' wires are

protected by circuit breakers which are mechanically coupled.

The Interfacing Card IFC-52 provides:

• All reference voltages and protection to the sub-modules.

• Signalization and manual interface (adjustment potentiometers

and test jacks) for the whole unit, and

• Communication with power system controller. Each of the sub-

modules consists of two cascaded power converters performing:

POWER FACTOR CORRECTION:

Power Factor (PF) correction circuit is based on a boost topology. The

boost converter has the inherent advantage of continuous input current

waveform which relaxes the input filter requirement. The performance of

the basic boost cell is improved by proprietary Snubber circuit, which

reduces the switching losses of the power semiconductor due to non-zero

switching times. Also the snubber circuit also decreases the

electromagnetic interference generated primarily during the turn off

process of the boost diode. The output of the boost converter is a

stabilized 400V voltage.

DC/DC CONVERSION: Further conversion of the stabilized high

voltage output of the power factor corrector circuit is necessary to

generate the isolated low voltage output and to provide the required

protection functions for telecommunication application. These tasks are

achieved in the DC/DC converter circuit, which is based on a full-bridge

topology. The full-bridge circuit is operated by phase-shift pulse-width

modulation with current-mode control. This control method provides zero

voltage switching conditions for all primary side power semi-conductor

effectively reducing switching losses and electromagnetic interference.

An advanced solution reduces the stresses on the output rectifier diodes.

Proper operation of the power converters is managed by supervised by

the housekeeping electronics. Remote commanding and monitoring of the

modules are possible through a power system controller.

3.

ESL-II (Electronics Switching Line)

CARD REPAIRING CENTRE : The card sent to the fieldwork, if damaged, during use are sent to the card repair center. The cards usually repaired are of the C-DOT DSS MAX exchanges, which are coming from all over India. The repair of the cards, which is currently on the work, is: -

LCC CCM TIC HNS

These various cards collected are from the centres at Lucknow, Delhi & KolKota. The Line Control Card is a terminal for the subscriber. The cards provide signaling interface towards terminal interface controller. These cards also feed current to the subscriber line.

The CCM card is similar to the LCC card except that there is an

extra Child card added for the metering purpose. In the card repair centre the testing of the card is done by the

interfacing software which work on the UNIX operating system. This software performs a number of tests on the card, which eventually helps the user to locate the area of the fault.

The main functional blocks, which are to be tested, are as follows: -

Amplification & Echo Suppression Current feed circuit Ring feed relay driver circuit Sensor and ring trip detection logic Signaling mux & scan/drive functions Voice multiplexing and selection Diagnostic function & active/ stand logic

Types of tests applied for the testing of the cards: -

1. Current test 2. On hook, off hook tests 3. Voice test 4. Ring test 5. Loop back test 6. Test access test 7. Copy 1 select 8. Copy 0 select 9. Battery reversal

10. TIC communication test

By running the above tests we can locate the problem up to block level if any of the above tests in a particular line fails. After the checking by the software the block or the area of the fault is located then the exact fault is identified by manual checking. Once the faulty component is located it is then replaced by a new component and the repaired card is again sending back to the field.

4. Surface Mount Technology

Surface mount technology (SMT) is the practice & method of attaching

leaded & nonleaded electrical components to the surface of a conductive

pattern that does not utilizes leads in feed through holes. Surface mount

technology is the latest trend in electronics manufacturing. It started way

back in 1986 that has been more than a decade now.

The need of SMT arises due to the following factors:

Need for SMT ▪ Automation The development of surface mount devices started a new era in

Electronics Manufacturing. Earlier the manufacturing process was too

complicated. The manufacturing process required lot of men, & time, but

thanks to the SMT that the manufacturing process can be fully automated.

The cards are manufactured through Design for manufacturing process

which can be a defined one. It has given rise to standardization so that all

the products made from a company perform same .

▪ Lowering Cost of Manufacturing

The cost of manufacturing has greatly reduced due to SMT. Earlier

lot of people were required for manufacturing now, a few can do the

same. The failures of manufactured equipments has greatly reduced due

to SMT. Also the prices for Through hole components were more than

the SMT, the defects were more in The traditional technology so we can

see how much does it effects the cost of manufacturing. We can see how

the prices for TV sets have greatly came down in the last decade.

▪ Reducing time to market

Due to automation the time required for manufacturing & then

sending to market has greatly reduced. We can see if the production time

would be more & demand is high as it is today then the prices would have

gone high for electronic gadgets. Also the Manufacturer’s have to lose

business due to this.This also has played a major role in development of

SMT in electronics.

Type of Surface Mount Devices There are various types of Surface Mount Components or

SMD (Surface Mount Devices) available in the industry .

1. Chip components: These components are very small size. These

consist of resistors, capacitors, diodes, LEDs etc.They are available as

small as0.6(l) x 0.3(w) mm .

2. SOTs: These are known as small outline transistors. This category comprises of components like, standard transistors, UJT, SCR, Triacs, Diacs, etc.

3. SOICs: These are known as small outline Integrated Circuits These are the ICs that can be directly mounted on the board with no requirement of insertion

4. TSSOPs: These are known as Thin Shrink Small outline Packages These are also ICs that can be directly mounted on the board but the pitch between pins very less of order 0.5mm & thickness of the ICs very thin of order 1.5 mm..

5. QFPs: These are known as Quad Flat Packages These are also ICs that can be directly mounted on the board but the pitch between pins very less of order 0.5mm & has pins on all four sides.

6. PLCC: These are known as Plastic Leaded Chip Carrier These are

also ICs that can be directly mounted on the board but these have J type

leads i.e. The leads are bend under the body of the IC. A PLCC has J-type

leads on all 4 sides & if it has a J-leads on two sided then it is called SOJ.

7. BGA: These are known as Ball Grid Array These are also ICs that can

be directly mounted on the board but these have leads in the form of balls

underneath the body. These BGAs are the latest trend in the SMT.

8. Surface Mount Connectors: These are the connectors which can be

directly mounted on the board. The connectors include connectors in

which PLCC, SOJ & BGA can be mounted.

For Other parts Vocabulary is given as under

• BGA Ball Grid Array • PPGA Plastic Pin Grid Array • BLP Bottom Leaded Package • QFP Quad Flat Pack IC • COB Chip on Board • QSOP Quarter-size SOP • COF Chip On Flex • SMC Surface Mount Component • COG Chip On Glass • SMT Surface Mount Technology • CPGA Ceramic Pin Grid Array • SFP Small form Factor Package • CSP Chip Scale Package • SOIC Small Outline IC • FCOF Flip Chip On Flex • SON Small Outline Non-leaded • FCOG Flip Chip On Glass • SOP Small Outline Package • LOC Lead On Chip • SOT Small Outline Transistor • LCCC Leadless Ceramic Chip Carrier • SSOP Shrink small-Outline Packag. • IPCs Integrated Passive Components • TAB Tape Automated Bond • MCM Multi Chip Module • TBGA Tape Ball grid Array • MELF Metal Electrode Face • TOB Tab on Board • PLCC Plastic Leaded Chip Carrier • TOF Tab on Flex • PGA Pin Grid Array • TOG Tab on Glass

5. GSM Technology

History of GSM

During the early 1980s, analog cellular telephone systems were experiencing rapid growth in Europe, particularly in Scandinavia and the United Kingdom, but also in France and Germany. Each country developed its own system, which was incompatible with everyone else's in equipment and operation. This was an undesirable situation, because not only was the mobile equipment limited to operation within national boundaries, which in a unified Europe were increasingly unimportant, but there was also a very limited market for each type of equipment, so economies of scale and the subsequent savings could not be realized.

The Europeans realized this early on, and in 1982 the

Conference of European Posts and Telegraphs (CEPT) formed a study

group called the Group Special Mobile (GSM) to study and develop a

pan-European public land mobile system. The proposed system had to

meet certain criteria:

• Good subjective speech quality

• Low terminal and service cost

• Support for international roaming

• Ability to support handheld terminals

• Support for range of new services and facilities

• Spectral efficiency

• ISDN compatibility

In 1989, GSM responsibility was transferred to the European

Telecommunication Standards Institute (ETSI), and phase I of the GSM

specifications were published in 1990. Commercial service was started in

mid-1991, and by 1993 there were 36 GSM networks in 22 countries.

Although standardized in Europe, GSM is not only a European standard.

Over 200 GSM networks (including DCS1800 and PCS1900) are

operational in 110 countries around the world. In the beginning of 1994,

there were 1.3 million subscribers worldwide, which had grown to more

than 55 million by October 1997. With North America making a delayed

entry into the GSM field with a derivative of GSM called PCS1900, GSM

systems exist on every continent, and the acronym GSM now aptly stands

for Global System for Mobile communications. The developers of GSM

chose an unproven (at the time) digital system, as opposed to the

then-standard analog cellular systems like AMPS in the United States

and TACS in the United Kingdom. They had faith that advancements

in compression algorithms and digital signal processors would allow

the fulfillment of the original criteria and the continual improvement

of the system in terms of quality and cost. The over 8000 pages of

GSM recommendations try to allow flexibility and competitive

innovation among suppliers, but provide enough standardization to

guarantee proper networking between the components of the system.

This is done by providing functional and interface descriptions for

each of the functional entities defined in the system.

Architecture of GSM Network A GSM network is composed of several functional entities, whose

functions and interfaces are specified. The GSM network can be divided

into three broad parts. The Base Station Subsystem controls the radio link

with the Mobile Station. The Network Subsystem, the main part of which

is the Mobile services Switching Center (MSC), performs the switching

of calls between the mobile users, and between mobile and fixed network

users. The Mobile Station and the Base Station Subsystem communicate

across the Um interface, also known as the air interface or radio link. The

Base Station Subsystem communicates with the Mobile services

Switching Center across the A interface.

Mobile Station :-

The mobile station (MS) consists of the mobile equipment (the terminal)

and a smart card called the Subscriber Identity Module (SIM). The SIM

provides personal mobility, so that the user can have access to subscribed

services irrespective of a specific terminal. By inserting the SIM card into

another GSM terminal, the user is able to receive calls at that terminal,

make calls from that terminal, and receive other subscribed services. The

mobile equipment is uniquely identified by the International Mobile

Equipment Identity (IMEI). The SIM card contains the International

Mobile Subscriber Identity (IMSI) used to identify the subscriber to the

system, a secret key for authentication, and other information. The IMEI

and the IMSI are independent, thereby allowing personal mobility. The

SIM card may be protected against unauthorized use by a password or

personal identity number.

Base Station Subsystem :-

The Base Station Subsystem is composed of two parts, the

Base Transceiver Station (BTS) and the Base Station Controller (BSC).

These communicate across the standardized Abis interface, allowing (as

in the rest of the system) operation between components made by

different suppliers.

The Base Transceiver Station houses the radio tranceivers that

define a cell and handles the radio-link protocols with the Mobile Station.

In a large urban area, there will potentially be a large number of BTSs

deployed, thus the requirements for a BTS are ruggedness, reliability,

portability, and minimum cost.

The Base Station Controller manages the radio resources for

one or more BTSs. It handles radio-channel setup, frequency hopping,

and handovers, as described below. The BSC is the connection between

the mobile station and the Mobile service Switching Center (MSC).

Network Subsystem :- The central component of the Network Subsystem is the

Mobile services Switching Center (MSC). It acts like a normal switching

node of the PSTN or ISDN, and additionally provides all the functionality

needed to handle a mobile subscriber, such as registration, authentication,

location updating, handovers, and call routing to a roaming subscriber.

The MSC provides the connection to the fixed networks (such as the

PSTN or ISDN). Signalling between functional entities in the Network

Subsystem uses Signalling System Number 7 (SS7), used for trunk

signalling in ISDN and widely used in current public networks.

The Home Location Register (HLR) and Visitor Location

Register (VLR), together with the MSC, provide the call-routing and

roaming capabilities of GSM. The HLR contains all the administrative

information of each subscriber registered in the corresponding GSM

network, along with the current location of the mobile. The location of

the mobile is typically in the form of the signalling address of the VLR

associated with the mobile station. The actual routing procedure will be

described later. There is logically one HLR per GSM network, although it

may be implemented as a distributed database.

The Visitor Location Register (VLR) contains selected

administrative information from the HLR, necessary for call control and

provision of the subscribed services, for each mobile currently located in

the geographical area controlled by the VLR. Although each functional

entity can be implemented as an independent unit, all manufacturers of

switching equipment to date implement the VLR together with the MSC,

so that the geographical area controlled by the MSC corresponds to that

controlled by the VLR, thus simplifying the signalling required. Note that

the MSC contains no information about particular mobile stations --- this

information is stored in the location registers.

The other two registers are used for authentication and

security purposes. The Equipment Identity Register (EIR) is a database

that contains a list of all valid mobile equipment on the network, where

each mobile station is identified by its International Mobile Equipment

Identity (IMEI). The Authentication Center (AuC) is a protected

database that stores a copy of the secret key stored in each subscriber's

SIM card, which is used for authentication and encryption over the radio

channel.

SERVICES PROVIDED BY GSM

From the beginning, the planners of GSM wanted ISDN

compatibility in terms of the services offered and the control signalling

used. However, radio transmission limitations, in terms of bandwidth and

cost, do not allow the standard ISDN B-channel bit rate of 64 kbps to be

practically achieved.

A variety of data services is offered. GSM users can send

and receive data, at rates up to 9600 bps, to users on POTS (Plain Old

Telephone Service), ISDN, Packet Switched Public Data Networks, and

Circuit Switched Public Data Networks using a variety of access methods

and protocols, such as X.25 or X.32.

FIG : FAX SERVICE

Other data services include Group 3 facsimile, as described in

ITU-T recommendation T.30, which is supported by use of an appropriate

fax adaptor. A unique feature of GSM, not found in older analog systems,

is the Short Message Service (SMS).

FIG : SMS - SHORT MOBILE SERVICE

SMS is a bidirectional service for short alphanumeric (up to 160 bytes)

messages. Messages are transported in a store-and-forward fashion. For

point-to-point SMS, a message can be sent to another subscriber to the

service, and an acknowledgement of receipt is provided to the sender.

SMS can also be used in a cell-broadcast mode, for sending messages

such as traffic updates or news updates. Messages can also be stored in

the SIM card for later retrieval.

GSM RADIO LINK

CALL ROUTING Unlike routing in the fixed network, where a terminal is

semi-permanently wired to a central office, a GSM user can roam

nationally and even internationally. The directory number dialed to reach

a mobile subscriber is called the Mobile Subscriber ISDN (MSISDN),

which is defined by the E.164 numbering plan. This number includes a

country code and a National Destination Code which identifies the

subscriber's operator. The first few digits of the remaining subscriber

number may identify the subscriber's HLR within the home PLMN.

An incoming mobile terminating call is directed to the

Gateway MSC (GMSC) function. The GMSC is basically a switch which

is able to interrogate the subscriber's HLR to obtain routing information,

and thus contains a table linking MSISDNs to their corresponding HLR.

A simplification is to have a GSMC handle one specific PLMN. It should

be noted that the GMSC function is distinct from the MSC function, but

is usually implemented in an MSC.

The routing information that is returned to the GMSC is the

Mobile Station Roaming Number (MSRN), which is also defined by the

E.164 numbering plan. MSRNs are related to the geographical numbering

plan, and not assigned to subscribers, nor are they visible to subscribers.

The most general routing procedure begins with the GMSC

querying the called subscriber's HLR for an MSRN. The HLR typically

stores only the SS7 address of the subscriber's current VLR, and does not

have the MSRN (see the location updating section). The HLR must

therefore query the subscriber's current VLR, which will temporarily

allocate an MSRN from its pool for the call. This MSRN is returned to

the HLR and back to the GMSC, which can then route the call to the new

MSC. At the new MSC, the IMSI corresponding to the MSRN is looked

up, and the mobile is paged in its current location area (see Figure 4).

Figure 4: CALL ROUTING IN GSM

6. Wave Soldering

RULES OF SOLDERING MACHINE:- Wave soldering machine, correctly controlled will be produce the highest quality joints at the lowest card.

1. Soldering is a process, will produce consistent results if properly

controlled.

2. Touch up the faulty soldered joint is costly, unreliable and

unnecessary.

3. Anything that reduces solder joints defects is cost effective.

4. Design handling, assembly and maintenance are all part of the soldering process and must be properly controlled.

5. Solder ability of boards and component accounts for 60% of all

faulty soldered joint.

6. Never use parts that fail solder ability testing, the ultimate cost is so high.

7. Soldering problems are solved by process control not move

inspection and touch up .

8. Everyone concern with soldering process must be formal and properly trained.

THEORY OF SOLDERING

Before we can discuss the details of the materials and

Machines used in the soldering process. It is essential that

the fundamental theory is clearly understood, without this

Understanding it will be difficult to visualize what occurs

When a solder joint is formed, and the effect of various parts

of a process. We will therefore focus the theory of as the first

part of Wave soldering. • Wetting • Soldering v Glueing • Wetting non wetting • Cleanliness • Capillary action • Pallet and conveyors • Controls The basic components of the Wave Soldering Machine are as followes: 1. Fluxer 2. Pre-heater 3. Solder Pot and Pump 4. Conveyor 5. Instrumentation and Controls

• Preheater

• Increase throughput (faster conveyor) • Reduce thermal shock (for chip caps) • Dry off flux (reduce blow holes) • Activate flux (better soldering results)

• Flux and Fluxer

• It applies flux. The flux is applied through Wave Foam Spray

• Wave Geometry • It has single & Dual wave. Single side is for through hole

components & dual wave is required for SMDs.