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Report on

One Months Industrial Training

At BHEL, Hardwar.

A Training Report submitted in partial fulfillment

Of the requirement for the award of degree of

Bachelor of Technology in

ELECTRONICS & COMMUNICATION ENGINEERINGOf Punjab Technical University Jalandhar.

Submitted by:

SHIPRA RASTOGI

(Roll No. 0829231037)

(Batch 2008)

Submitted to:

Mr. Anand Thakar

AGM(Telecom)

Department of

ELECTRONICS & COMMUNICATION ENGINEERING

MEERUT INSTITUTE OF TECHNOLOGY, MEERUT

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CERTIFICATE

This is to certify thatMiss SHIPRA RASTOGIhas undergone four

Weeks training here in our organization Bharat Heavy Electrical

Limited, Hardwar (UK). Her discipline and performance during the

training period was excellent. We wish him a very prosperous and

bright career in future.

(ANAND THAKAR) (V.K. JOSHI)

AGM Mtr. TECH

(WEX-TELECOM) (WEX-TELECOM)

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ACKNOWLEDGEMENTS

First and foremost, I would like to thank my respected parents, who always encouraged me and

taught me to think and workout innovatively what so ever be the field of life. My sincere thanks

goes to Mr. Anand Thaker (AGM) Telecom for his prodigious guidance, persuasion, and

painstaking attitude, reformative and prudential suggestion throughout my summer trainingschedule.

Special thanks go to Mr.V.K.Joshi (Sr.Technician) Telecom. Who helped me a lot in

giving minute details of Telecom. Department and enlightened me with the knowledge ofExchange equipments and their working.

Last but not the least, my sincere thanks to all the staff members and friends for instilling in me a

sense of self-confidence.

BRANCH: (ELECTRONICS & COMM. ENGG.)

Academic Year:2008-2012

Institute :MEERUT INSTITUTE OF TECHNOLOGY,MEERUT

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TELECOMMUNICATION SYSTEM IN BHEL, HARDWAR.

VOCATION TRAINING REPORT: 2008

CONTENTS

1. Introduction.

2. The Organization.

3. Telecommunications.

4. Electronic Exchange(s).

5. Telephone Lines.

6. Connection Types.

7. General faults occurring in an Exchange.

8. Special User Features of Various Exchanges.

9. Optical Fiber System.

10. Maintenance.

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1.INTRODUCTION.

In past few years the field of communication has been developing with no leaps or bounds. It has

become a necessity of each human being to be connected with each other. Telephone is rapidly

becoming a tool to quench this thirst.

In Automatic Telephony, operators are not required to establish connections manually between the

different calling and the called subscribers as are required in the case of manual telephone systems.In these system subscribers those selves establish required connections by operating the different

switches placed at the central place known as the EXCHANGE from their telephones at remote

place from it. The automatic telephone systems are rapidly replacing manual ones due to theiroutstanding merits over the latter types, some of which are enumerated below:

* In Automatic Telephony higher level of secrecy is maintained due to absence of

Operators who can overhear the conversation if they like in the manual telephone

Systems.The working of an Automatic Telephone system does not depend for its efficiency

On the personal efficiencies of the operators.

* There is no possibility of the calls being missed or wrong metering being done due to faults of

operators or due to phonetic errors between the subscribers and the operators.

As no operator is required, the running cost of the exchange is reduced.

COMMUNICATION Dia.I

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2.THE ORGANIZATION.

BHEL was primarily set up to meet the needs of the power sector in the country. The firstplant was established nearly 35 years ago at Bhopal, which heralded the genesis of the heavy

electrical equipment in India. BHEL is today the largest engineering enterprise in India, with

excellent track record of performance, making profits continuously since 1971-72. It achieved a

sales turnover of Rs. 3154 carores with a pretax Profit of Rs.201 carores, in 1990-91.

The areas of BHEL operations broadly cover conversion, transmission, utilization and

conservation of energy in core sectors of the economy like Power, Industry and Transportation,

etc., and fulfill vital infrastructure needs of the country.

Today, BHEL has 13 manufacturing divisions, 8 service centers and 4 Power Sector

Regional Centers, in addition to over 150 project sites spread all over India and even abroad to

provide prompt and effective service to customers.

BHEL Hardwar is one of the premier organizations which is honored by I.S.O.-9002specifications.

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3. TELECOMMUNICATION.

BHEL manufactures EPABX and MAX systems based on C-Dot technology and has plans

to make other ranges of telecommunication equipment also.

These are basically used for connecting links between various modules like peripherals, exchangeand its equipments. It is necessary to run a number of internal cables of suitable conductors

between the following stages and frames:-

1. Handset to exchange's cable chamber

2. Cable chamber to M.D.F.

3. M.D.F. to I.D.F.4. I.D.F. to Number Block

5. Number Block to Exchange Equipment

6. Between two exchanges

7. Between two cities

8. Between two countries

Prior to advent of Electronic Exchanges inter-connection of various circuits are made bymechanical contacts that are operated by mechanical movements produced by the attraction of an

iron armature of an electromagnet or by the operation of an electric motor. There are some

disadvantages of such systems for using mechanical contacts, due to following reasons:

Contacts are subjected to wear and tear.

Require adjustments time to time.

Maintenance is highly precise.

Prone to corrosion. Etc...

But now-a-days Electronic Exchanges are used. In Electronic exchange electronic devices effectthe inter-connection between different transmission circuits and Electro-mechanical relays and

switches are dispensed with. Such electronic devices remove difficulties associated with

mechanical contacts. The greatest advantage of using electronic devices in place of

electromechanical devices is that no time is loosed in making a connection and a very high speedof operation is possible.

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4. ELECTRONIC EXCHANGES.

Electronic Exchanges are of two types:

1. Tone type

2. Pulse type

1. Tone type: In this type of exchange sine waves are used. There speed of dialing for a given

number is more than that of Pulse type.

2. Pulse type: In this type of exchange square wave is used due to which the dialing speed is

lesser. The telephone apparatus used for both types are different in construction. But now daysboth types of apparatus are integrated in a single machine in which switch-over can be made via a

selector switch.

TONES USED IN MODERN TELEPHONY

Dial Tone: When handset is picked up from the cradle, then Dial tone is heard if a free line isavailable. This means that the instrument is ready to send the signals to the exchange. When the

subscriber takes up the receiver then signals are sent M.D.F. then to I.D.F., line Number block and

to Peripherals where in various line-cards are mounted in a shelf. When corresponding number onthe line-card is free then the Ringer section of that Peripheral generates a signal called tone. This

tone is a continuous burble sound of 400 Hz. modulated by 25Hz. and is sent to the calling

subscriber as soon as his line seizes the free line. The subscriber must not dial before receiving thistone; otherwise he is liable to get wrong connection. If he does not get this tone, he should try after

some time.

Busy Tone: When the called subscriber is engaged with other call, this tone is heard. It consists ofa sound of 400 Hz. which is regularly interrupted at equal intervals. It is generally on for 0.75 sec.

and off for also 0.75 sec.

Ringing Tone: When a number is dialed then telephone of the called subscriber starts ringing.

Calling subscriber should get this information and this is indicated by sending ringing tone of

interrupted 400 Hz. supplies modulated by 25 Hz. and its durations are generally equal to theduration of ringing current, which rings the bell. It may be 0.4 sec. on, 0.2 sec. off , 0.4 sec. on and

2 sec. off and so on or it may be 0.75 sec. on and 0.75 sec. Off and so on. When this ringing tone

is received, the calling subscriber knows that the connection is completed and that the bell of thecalled subscriber is ringing.

Number Unobtainable Tone: This tone is sent when the number dialed cannot be obtained. If any

subscriber dials which is not actually connected to the exchange, this indication is send. This isalso a tone of 400 Hz. with interruption of 200 msec. every 3 sec.

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Now-a-days push button type telephone apparatus are used. This apparatus can be exploded into

following sections:1. Ringer section

2. Speech section (Transmitter and Receiver section)

3. Voltage limiter section

From telephone exchange two wires or connectors run for each number, in which one is neutraland the other is main or positive. For the telephone circuit to work the necessary supply is

provided by the exchange. Like other circuits telephone also operates when a circuit is established

between calling and called subscriber. When one dials a number then the corresponding relays atthe exchange established a circuit automatically. The telephone exchange supplies 40-60 volt D.C.

and 110/20 Hz. to operate this circuit. This is required because of voltage drop that may creep in

long transmission wires. As soon as the handset is picked-up this 48-volt D.C. supply is availableat voltage limiter section, dialing pulse generator and speech section.

In telephone dialing two types of frequencies are used which are:

* High band tone (1216 Hz. to 1645 Hz.)

* Low band tone (701 Hz. to 936 Hz.)

Frequencies used in Telephony

The numbers from 1 to 5 falls in low band and 6 to 9, 0 falls in high band. Till the handset is on-

hook, the ringing section of the apparatus is on through telephone line but on lifting the handset theringing section becomes off, also the dialing and speech section becomes ready. On lifting the

handset first the dial tone is received which is amplified by the amplifier of speech section.When a number is pressed on the keyboard, the dialing pulses are made on and off according to the

number dialed. For example if 5 is pressed then dialing pulses are made on and off 5 times. This

process can be heard on the receiver. There is a gap of 1 sec. between consecutively pressed

numbers.When the handset is placed on or is lifted from the instrument a switch is operated called the hook-

switch. The main function of this switch is to toggle between telephone-line and ringer, dialing &

speech sections of the telephone. When the handset is on the telephone then ringer section of thetelephone is on while on lifting it ringer section is disconnected and dialing section is connected.

How the telephone call is made:

Telephone call is characterized into two sections:

1. Outgoing calls: Generally a voltage of48V-60VD.C. always remains on the telephone line but

as the handset is picked-up the voltage limiter drops this voltage to 9-12V. On hearing the dial toneit is confirmed that the apparatus is ready to work and after dialing the number a ringing pulse is

send to the called party. When the calling party picks-up the handset the billing meter of the

exchange becomes activated. There is a counter in the exchange, which counts the pulse andconverts them into calls.

2. Incoming calls: These are just opposite of outgoing calls. In the incoming calls the telephonedetects the ringing signal from the exchange and provides the ring. At the instance of ringing

signal, there remains a voltage of 75-110V./20 Hz. on the telephone. A high voltage (A.C.) is sent

from the ringer section of the exchange to start the ringer circuit of the telephone. When theringing signal is received it should be properly isolated as it may give a shock. This ringing circuit

is on until the handset is not picked-up at the called party. The duration of this tone, if unattended,

is 1 minute after which an engage tone is heard. After lifting the handset a circuit is established and

a call is made.

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Electronic Exchange Dig.II

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There are various powers providing circuits available in the exchange to run the circuitry. Theseare broadly categorized in two categories:

* Outside the exchange

* Inside the exchange

Outside the Exchange:

Since the voltage supplied in Indian Subcontinent is 220-volts/50 Hz. A.C. but for the normal

working of the exchange 48(46-53) volts of D.C. is required.

Hence a Rectifier circuit, backed with battery array for power-failures, is used. Thisrectifier block not only rectifies the input supply but also works as a battery charger. It is known

as Float rectifier cum charger.

Battery backup is utilized for smooth operation of the exchange during power failures. For batteryback-up lead acid battery array is used in parallel to the supply from the rectifier block, so that

during power failures the exchange supplies are not terminated.

Inside the Exchange:

Inside the telephone exchange various types of power supplies are used for powering variousmodules (for example: - Line-cards, Ringer). Some of them are: -

# -5 V. 12 A

# +5 V. 12 A

# +12 V. 6A.

From M.D.F. a number of cables, based upon the requirement of a place, are connected to

cabinets. On the cabinets these cables are divided into cables of 20 pairs. Now every 20 pair cable

goes to the distribution box (D.B.). At the D.B. this 20 pair cable is further divided into two parts

of 10 pairs each. These pairs are then connected to the subscriber ports via jumpers. The line fromthese ports then goes to the subscribers through single pair cables which are usually of P.V.C. type.

These wires are connected to the instrument via Rosette-Box.

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M.D.F.: -This frame serves the following purposes: -

It is place where both external and internal cables are terminated. The external individuals

cable carry conductors from subscribers who are necessarily from the same locality and as suchtheir numbers cannot be in numerical order. On the other hand, the internal cable conductors

come from apparatus side in numerical order. This cross-section between the two cables is

done on the M.D.F. through jumper wires.

It carries all the protectors used in the exchange. The different protectors that are used are (a)

Fuses, (b) Heat coils, and (c) lightning protectors.

This M.D.F. is an ideal place for testing purpose. Both the internal and the external cablesare available at this frame and, therefore, both external and internal wiring and lines can be

tested for this purpose.

I.D.F.: -These frames like M.D.F. consists of a large number of verticals with horizontal cross-arms

fitted with tag blocks at both the ends. The cable from M.D.F. is terminated on the multiple sides

from where connections are extended to metering and from the exchange side cables are run to therespected line-cards. The two tag blocks are joined by means of jumper wires as in the M.D.F., so

that any subscriber can be given connection to any uniselector on the line-card. The subscriber and,

therefore, their uniselector are divided into different groups and it is necessary for these groups tooriginate more or less the same amount of traffic for smooth distribution among different trunks.

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NEW MDF Dig.III

OLD MDF Dig.IV

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5. TELEPHONE LINES.

In BHEL-Hardwar three types of telephone lines are used. They are: -

MAX Lines

EPABX Lines

C-DOT Lines

MAX Lines:

Before MAX Ex. Lines are used only Internal Exchange. But New (CORAL) MAX lines

are used for both internal (Intercom) and external communication links BHEL.

EPABX Lines:

EPABX lines are used for both internal and external communication links in BHEL. If the

user wants to dial outside the periphery of BHEL, he can use these lines. There are about 500 lines

available here. These lines are distributed in 17 line-cards with 24 line numbers in each. Its I.D.F.section has 40 tag blocks. 96 numbers available here are connected via digital lines in which a host

of facilities are provided that can be accessed using code 69.

C-DOT Lines:These lines are the direct telephone lines from C-DOT The facility they provide is called

DID (Direct Inward Dialing). It has 24 lines and any BHEL number starting with digit 5 can be

accessed using code 48.

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6. CONNECTION TYPES.

Types of Connections:* With wires i.e. Cables

* Wireless Microwave Links through Satellite

Cables: Two types of Cables are used. They are:

1) Underground cables: These types of cables run under the earth and are basically used to connect

the exchange to the subscriber's Distribution Box (D.B.). They are further of two types based upontheir construction and the insulating material used.

a. Paper core A.T.C. (Armored Tin Cable)b. Jelly filled A.T.C. (Armored Tin Cable)

2) Overhead cables: These types of cables are used to connect the equipments inside the exchange

and to connect the peripheral devices to the subscriber's Distribution Box(DB) They are generally of P.V.C. type.

In an exchange, based upon the number of conductor pairs, following types of cables are used:

* Single Pair cable* 2 Pairs cable

* 5 Pairs cable

* 10 Pairs cable* 20 Pairs cable

* 50 Pairs cable

* 100 Pairs cable

Color-coding:

TYPE OF CABLECOLOR OF WIRES

Single pair Blue-White

2 Pair cable Blue-White/Orange-White

5 Pair cable Blue-White/Orange-White/Green-White/Brown-White/Grey-White

10 Pair cable Blue-White/Orange-White/Green-White/Brown-White/

Grey-White/Blue-Red/Orange-Red/Green-Red/Brown-Red/Grey-Red

20 Pair cable

Blue-White/Orange-White/Green-White/Brown-White/Gray-White/Blue-White-Blue/Orange-White-Blue/Green-White-Blue/Brown-White-Blue/

Gray-White-Blue/Blue-White-Orange/Orange-White-Orange/Green-White

-Orange/Brown-White-Orange/Gray-White-Orange/Blue-White-Green/Orange-White-Green/ Green-White-Green/Brown-White-Green/

Gray-White-Green.

For 100 pairs cable the color-coding is same as that of the above 20 pairs cable exceptThat the mate color is changed after each bunch of 20 pairs.

PAIRMATE COLOR1st 20 pairs White2nd 20 pairsYellow3rd 20 pairsBlack4th 20

pairsViolet5th 20 pairs Red

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7. General faults occurring in an Exchange.

There are mainly two types of faults that often occur in the Exchange. These are basically

* Faults that occur from Line* Faults that occur due to Instrument

A. Faults that occur from Line:

Due to line three types of faults may occur. They are categorized as under:

1. Break fault: They are also called as Disconnection faults. They can occur in the connectors athome, in line or in exchange. In common they are broadly called as "Telephone is dead".

2. Loop fault: They are also called as Line-Shorting faults. In this fault connectors are shorted

prior the instrument forming a local loop. If unattended for a long time they may cause severedamage to the Exchange.

3. Earth fault: This fault may occur due to:* wetting of connectors

* Water in Rosette-Box

* Weak insulation or

* Oxidation of copper wireConnectors can either touch from earth, with other connector or with any conductor (such as

metallic table, frame etc.)

Problems that can occur due to line faults:

1. Subscriber can not dial a number.

2. Ring Trip i.e. connection from the exchange breaks after one ring.

3. False Ring4. Low speech

5. One sided speech

Faults that occur due to instrument:

These may be:* The number is not being dialed

* One way speechReceiver coil is faulty

Faults that occur due to instrument: contd

* Plunger or Push switch faulty. Dial tone breaks after two or three rings.

From second subscriber bell is heard to be going but at first subscriber only dial toneIs heard.

* Instrument circuitry faulty.

When loop or earth fault is received than exchange can be affected so it is wedged as soon aspossible because if not wedge for longer it can damage line-card too.

To sense these faults first line-side is checked and then exchange side is checked at

exchange. If however exchange side is correct then line faults after detection are handed over tothe concerned lineman for further checking.

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Testing Procedure Dig.V

Testing Procedure Dig.VI

Testing Procedure Dig.VII

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Testing Procedure Dig.VIII

Testing Procedure Dig.IX

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Testing Procedure Dig.X

Testing Procedure Dig.XI

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Testing Procedure Dig.XII

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8. LIST OF SPECIAL USER FEATURES ON VARIOUS EXCHANGES.

A) MAX (CORAL INDIA PVT.LTD.NOIDA)

Manufacturer: - JEUMONT SCHINEDIER, FRANCE

Capacity: - 2700 lines

CALL PICK UP: 89-xxxx to pick up a call ringing at another location xxxx.

CALL TRANSFER: 2 Parties conversing, any party can dial 3rd party, thenConversation among them Hang-up. The party on line now

Talks to 3rd party.

PARTY CONFERENCE: While speaking with a party:

(From Pulse Instrument: -- If CALLER requires dialing 3rd party

During conversation and maintaining talks, then dial 4.

(From Tone Instrument: -- If CALLER requires dialing 3rd party

During conversation and maintaining talks, then flash, and dial 4.

MALICIOUS CALL TRACE: Dial 29 during conversation, to trace a

malicious call From a MAX Extension. Then enquire from 4999 or 4424.

APPOINTMENT REMINDER: Dial 80-xx-yy {xx=hr, yy=min}.

To Cancel: Dial 27.

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LIST OF SPECIAL USER FEATURES ON VARIOUS EXCHANGES Contd

B) EPABX=ALCATEL 4400

Manufacturer: - ALCATEL, FRANCE

Capacity: - 500 lines (96 DIGITAL, 404 ANALOG)

Technology used: - P.C.M. - T.D.M.

1. TONE MODE DIAL: Dial # before no.{If instrument is not tone enabled )

2. CALL TRANSFER: Hook FLASH: Do Hook Flash -

On hearing prompt "Please dial." Dial the no., wait for party to respond, then

Disconnect.

3. ENQUIRY CALL: FLASH (from Tone mode instrument.) or 2 (from Pulse mode)

During converses, to put the party on HOLD. Then, dial a 3rd party and speak.

4. BROKER CALL: (After ENQUIRY CALL): Dial 1

To go BACK & FORTH, between two parties (one party in conversation & other

On HOLD)

5. CONFERENCE-3 PARTY: While talking to 1st party, first make ENQUIRY CALL

(Put on hold){FLASH from Tone; or 2 from Pulse}.Then - Dial 3rd party - Flash-- Dial 3.

6. AUTO CALLBACK: Dial 5 to book auto-callback when a busy PABX hangs up.

( To cancel auto-callback request: Dial 67 or/and 848)

7. PASSWORD MODIFICATION: 847-0000-xxxx (0000=old password; xxxx = new

Password). This facility is available on STD enabled extensions only.

8. LAST CALLER CALLBACK: 851 {to ring the last unattended PABX Caller}

9. APPOINTMENT REMINDER: 852 then dial the time as {xx (hr) xx (min)}

To cancel: 853

10. LAST NO. REDIAL: 854 User can use this if instrument. Doesnt have a RedialButton.

11. CALL PICKUP: 72 - XXXX to pickup a call ringing at another extension.

12. CALL-PARK / RETRIEVE: It is used during an incoming or outgoing call, to speak

From a different set.(To park from own (speaking) set: FLASH-855- dial own extension number. Then

"Hang-up". The call is now parked, and the other party is kept on hold.

(To pick up from a different set: 855- dial own extension number)(To pick up from own set (later, if not taken elsewhere) 855)

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9. OPTICAL FIBER SYSTEM.

Fiber optical transmission medium is fast emerging as an alternative and strong competitor

to coaxial cables in telecommunication networks.

Long distance data transmission in electrical cables suffers from ground loop problems.

The merits of the optical fiber stem from the fact tat the basic material used in their construction isnonmetallic and electrically non conductive.

In contrast, the nonmetallic and totally dielectric fiber optical cable are immune to radio

frequency an other electromagnetic interferences. Ground loop and common mode voltage

problem do not exist and data can be transmitted between points of vastly different potential. Inoptical cables the information is transmitted by packets of photons which have no charge. There is

no possibility of sparks or short circuit when a fiber is cut. The bandwidth high compared to that of

the electrical cables. The standard RG-58 coaxial cable has bandwidth distance product of a typicaloptical fiber is about 100 MHz-Km.

Fiber cables are about the thickness of a human hair any dirt obstructing the optical port causespoor transmission. The thin dimension results in a low weight for given length when compared to

electrical cables. However, being thin and somewhat brittle in nature, fiber tend to break easily if

bent beyond a certain limit a direct viewing into the optical point can be harmful to the eyes.

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10. MAINTENANCE.

The subject of maintenance of Automatic Telephone Exchange can be broadly divided under two

categories: -

1. Prevention of Service Failures.

2. Location of Faults and their removal.

Prevention of Service Failures can be done in following ways: -

1. Suitable design and adoption of suitable adjustment standards of the equipment parts of the

exchange can minimize failures in service.

2. Some preventive measures may also reduce service failures viz. keeping the rooms dust free,

maintaining temperature and humidity under tolerable limits using air-conditioners etc...

3. Routine inspection, routine tests and routine adjustments also help in preventing service failures.

When faults occur in some parts of the exchange, they should be detected and removed as quickly

as possible.

Various tools are also used to check the faults in the telephone lines.

For checking fault inside the exchange