INDEX

1. ABSTRACT

2. PROFILE OF VISAKHAPATNAM STEEL PLANT

3. INTRODUCTION TO COMMUNICATION SYSTEMS IN VSP

4. PRINCIPLES OF TDM- PCM

5. THE 3000 LINES PLANT EXCHANGE

POWER SUPPLY AND BATTERY

SWITCHING SYSTEM

Features

System controller

System configuration

M.D.F

6. ADVANTAGES WITH MODERN ELECTRONIC EXCHANGES

7.CONCLUSION

1

ABSTRACT

The title of the project is “WORKING OF TDM-PCM BASED

3000 LINES ELECTRONIC EXCHANGE “ the project aims at studying

the various units employed in the electronic exchange right from

construction phase to implementation and operation phase.

The project is undertaken at the Visakhapatnam steel plant.

The plant electronic exchange is installed by ALCATEL-LUCENT and

has been built with Technology of FRANCE. This model exchange is

designed initially for 3000 subscribers and is capable of extending

beyond 10,000 at a later stage. The report mainly covers the

different types of Communication Systems that are used in

Visakhapatnam Steel Plant , Basic principles of Electronic Exchanges

and about 3000 lines VSP-Plant exchange its working principle,

different components and its advantages.

In this exchange we study about the following main parts such as:

Power Plant, Main Distribution Frame, and Switching System.

Battery provides the back up for the power plant, in case of any power failure.

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In the switching system we study about the control cards and pheriphral cards.

Basically this exchange is an ISDN exchange, which means

“Integrated Services Digital Network” exchange. That means this

exchange supports voice signals as well as data and video signals.

There by the capabilities of the exchange is enhanced compared to

older type electronic exchanges.

This exchange is a micro processor based one, which

employs “CPU7-2” Processor for its call-processing and switching

functions.

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ENVIRONMENT OF VISHAKAPATNAM STEEL PLANT

ABOUT THE ORGANIZATION:

Vishakhapatnam Steel Plant the first coastal based steel plant

of India is located 16 kms south west of city of destiny. Bestowed

modem technologies VSP have an installed capacity of 3 million tons

per annum of liquid steel 2.66 million tons of salable steel. At VSP,

there is emphasis on total automation seamless integration and

efficient up gradation, which results in wide range of long and

structural products. To meet stringent demands of disceming

customers with in India and abroad. VSP products meet exalting

international quality standards such as JIS, DTN, BIS and BS etc.

VSP has the distinct to be first integrated steel plant in India to

become an ISO-9002 certified company. The certificate covers

quality systems of operational, maintenance, and service units

besides purchase systems, training and marketing functions

spreading over four regions regional marketing offices, 20 branch

offices and 22 stock yards located all over the country.

VSP by successfully installing and operating efficiently Rs 460

cores worth of pollution Control and environment control

equipments and converting the barren landscape by planting more

than thee million plants has made the steel plant township, and

surrounding areas in to a Heaven of lush greenery. This has made

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steel township a greener, cleaner and cooler place which can boost 3

to 4 degrees centigrade lesser temperature even in peak summer

compared to Visakhapatnam city.

In addition to these VSP exports quality pig iron & steel

products to Sri Lanka, Myanmar, Nepal, Middle East, USA, South East

Asia. The Visakhapatnam Steel Plant was awarded “Star Trading

House“ status during the period 1997-2000. Having established a

fairly dependable export market, VSP plans to make a continuous

presence in the export market. It has also won the “National Safety”

award for the year 2003 for having followed the best safety rules.

Having a total manpower of about 18,000 VSP has

envisaged a labour productivity of not less than 230 tones of liquid

steel per man every year, which is the best in the country and

comparable with the International standards.

Some of the salient state-of-the-art technologies in VSP are:

7 meter coke oven batteries with coke dry quenching.

Biggest blast furnace in the country.

Bell-less top charging system in blast furnance.

100% slag granulation at the BF cast house.

Supressed combustion-LD gas recovery system.

100% continuous casting of liquid steel.

5

“Tempcore” and “stelmor” cooling process in LMMM and

WRM respectively

Extensive waste heat recovery system.

Comprehensive pollution control measures.

VISION AND MISSION :

VISION:

To be a continuously growing world class company .

We shall

Harness our growth potential and sustain profitable growth.

Deliver high quality and cost competitive products and be

the first choice of customers.

Create an inspiring work environment to unleash the

creative energy of people.

Achieve excellence in enterprise mangement.

Be a respected corperate citizen, ensure clean and green

environment and develop vibrant communities around us.

MISSION :

To attain 10 million ton liquid steel capacity through

technological upgradation operational effeiciency and exapansion ;to

produce steel at international standards of cost and quality; and to

meet the aspiration of the stakeholders.

ZONES IN VSP:6

The entire steel plant is divided into various zones such as,

RAW MATERIAL HANDLING PLANT(RMHP):

The RHMP receives the basic materials iron ore fluxes(lime stone,

dolomite), coking and non-coking coals etc. requires for the steel

making process from various sources through vagons which are

stacked and reclaimed by stackers-cum reclaimers and distributed to

various departments of vishakapatnam steel plant through conveyor

systems.

COKE OVENS:

These tall ovens takes raw coal as input and produces coke by

processing the coal in the absence of air or oxygen. This shop

manufactures and supplies coke, a hard porous solid fuel for blast

furnaces.

Coal is converted into coke by heating the prepared coal blend

charge in the coke ovens in the absence of air at a temperature of

1000-1050 degree centigrade for a period of 16-18 hours.

Red hot coke is pushed out of the oven and sent to coke dry

cooling plants for cooling to avoid its combustion. They are 3 coke

dry cooling palnts(CDCP) ech having the four cooling chambers. The

capacity of ecach cooling chamber is 50-52 TPH nitrogen gas is uses

as the cooling medium. The heat recovery form nitrogen is done by

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generating steam and expanding in two back pressure turbines to

produce 7.5 mega watts power each.

The coal chemicals such as benzole, tar, ammonium sulphate, etc are

extracted in coal chemical plant from co gas. After recovering the

coal chemicals the gas is used as a by-product fuel by mixing it with

gases such as BF gas,LD gas etc.

Facilites:

There are 4 batteries, each having 67 ovens.

The volumetric capacity of each oven is 41.6 m3.

Dry Coal charge /Oven is 32 t

Salient Features:

Largest and technologically unique Coke Oven Batteries in the country at the time of commissioning.

7 metre tall coke ovens batteries.

Selective crushing of coal to improve the coke quality.

100% Dry Quenching of coke using Nitrogen gas.

Power generation, from the waste heat recovered, at BPTS (Back Pressure Turbine Station).

Capacity :

Production capacity – 2.635 Mt of Gross coke per annum (2.261 Mt of BF Coke per annum).

8

SINTER PLANT(SP):

There are two sinter machines each of 312 sqmt great area. Here

iron ore fines, coke breeze, lime stone, dolomite are mixed together

to form the agglomerated mass, called gross sinter which is used in

the blast furnaces as the promary input the annual production

capacity is 5.256 MT per annum in sinter.

BLAST FURNACES(BF):

Pig iron or hot metal produced in the blast furnace. The furnace is

run with blast at high temperature and pressure of 1500 deg. Raw

material required for pig iron and iron or iron making ore, sinter,

coke, and lime stone. They are two 3200 cubic meter blast furnaces

equipped with bell-less top charging to meet 3.0 MT annual metal

requirements. Each furnace is provided with a set of four hot blast

furnace stoves designed for supplying air blast up to 1300 deg.c.

Three turbo blowers,one for each furnace and one stand by common

to both furnaces are provided with 12 MW top pressure recovery

turbo generating power.BF gas produce from each furnace is cleaned

in gas cleaning plant comprising dust catcher,high pressure scrubber

and is distributed throughout the plant as a fuel.

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The output of this furnace is liquid iron and can be casted directly

into pig shaped mould called pig iron or can be sent to Steel Melt

Shop for further steel making process.

STEEL MELT SHOP(SMS):

A place where the quality of steel is improved by heating and

oxygen lancing process. Steel is an alloy iron and carbon,where

carbon should be less than 2%. Hot metal produced in BF contains

impurities like carbon, sulphur, phosphorous, silicon ect.., this

impurities will be removed in steel making by oxidation process.

these are the three L.D convertors to conert the hot metal into steel.

The steel melt shop complex comprises of two 1300-ton hot metal

mixers, three 130-ton LD convertors and six 4 stand bloom casters.

Each covertor is being provided with gas cleaning palnt for cleanng

and recovery of LD gas, which will be used as fuel in plant. The

output of this plant is called Liquid steel or blooms are formed which

is further sent to mills area for shaping in different formats.

ROLLING MILLS:

A sophisticated, high capacity, high speed, fully automated

mills, which gave final shape to the steel products. Blooms cannot be

used as they are in daily like. These blooms have to be reduced in

size and properly shaped to fit for various jobs. Rolling is one of the

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machanical process to reduce large size sections into smaller ones.

The cast blooms from CCM are heated and rolled into long products

of different specifications like high capacity, sophisticated high speed

rolling mills. The roling mills complex comprises:

LIGHT AND MEDIUM MERCHANT MILL(LMMM): It includes the

billet mill and bar mill. It has a two strand rolling mill. which

produces billets, bars, and structures. The annual capacity is

1.857 mts of billets and 7.1 mt of bars and structures.

WIRED ROD MILL(WRM): It is a high speed four strand

continuous mill the mill is designed to produce wire rods in

plane rounds and ribbed bars(5.5 to 12.7 mm diameter). The

annaual capacity of wired rods production is 0.8 mt.

MEDIUM MERCHANT AND STRUCTURE MILL(MMSM): This

mill nproduce squares 12 to 65 mm, flats 30 to 150 mm,

channels and angles etc… this mill has a annual capacity of 0.85

mt of structures bars and angles.

THERMAL POWER PLANT (TPP):

The estimated power reuirement for V.S.P in

280 at 3.0 MT stages, the peak load being 292 MW essential loads

being 49 MW. The generating capacity is 286.5 MW . in this plant,

6000 Nm³/min turbo blowers are being provided supplying cold air

blast frunace.

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COMMUNICATIONS SYSTEM OF V.S.P

The success of Visakhapatnam steel plant is attributed mainly to its

proper management of communication. Communication plays a vital

role in coordinating the activities of various departments in achieving

the assigned targets and accomplishing the desired performance.

The telecommunications department in VSP is catering for the

communication needs of the steel plant and township area for the

past 22 years. In steel plant, very wide range of communication

systems is provided for meeting the day-to-day internal and external

communication needs.

INTRODUCTION TO COMMUNICATION SYSTEMS

INTRODUCTION:

The term communication system refers to the sending,

receiving and processing of information by electronic means. As

such, it started with wire telegraphy in 1840’s developing with the

telephony some decades latter and radio at the beginning of the

twentieth century. Radio communication made possible by the

invention of the triode tube, which became more widely used and

refined through the invention of transistor, integrated circuit and the

semiconductor devices. More recently the use of satellites and fiber

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optics has made communication system more wide spread with an

increasing emphasis on computer and other data communication.

A modem communication system is first concerned with the

sorting, processing and storing of information before its

transmission. The actual transmission then follows with further

processing and filtering of noise. Finally we have reception, which

may include processing steps as decoding, storage and

interpretation. The various forms of communication at present

includes radio telephony, telegraphy, broadcasting point to point

and mobile communications, computer communications, radio

telemetry, radar and radio aids to navigation.

The invention of telephone in 1876 has marked revolution in

world’s telecommunication system. Soon it developed such that

today, telephone network is far-flung highly complex and highly

integrated ‘system extending into almost every nook and corner of

all industrialized countries.

In earlier stages telephone switching was done manually.

Modem switching is effected automatically as on the Strowger,

Crossbar and electronic system of interconnection. These systems

operate on the principle of common control with incoming pulses

temporarily stored in the device, which then controls the switches

directly or indirectly. In the recent past telephone dialing is done

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with out the aid of operators. In this system switching mechanism

selects the route to distant telephone and if it finds the direct circuit

busy, it explores in succession a number of alternate route and

establishes the connection over the least circuitous path.

Further progress in the transmission is in the direction of digital

rather than analog techniques. Speech signals will be multiplexed by

the pulse methods with channels interleaved in time instead of

frequency. The most promising method is pcm, which provides at

the expense of bandwidth low vulnerability to interface and makes it

possible to regenerate pulses perfectly at each repeater, so that

there is no accumulator distortion and hence no noise and cross talk.

In contrast to electro-mechanical switching system, electronic

system will afford a high degree of versatility through the program

stored in the memory. Before long facilities will be available to have

features such as simplified codes for reaching frequency called

telephones subsequent automatic completion of calls to a busy

specified telephone, automatic centralized answering and like type.

More recently, communication satellite, employing microwave

techniques are increasingly used to handle several thousand voice

channels with the advent of the devices like traveling wave tube, the

maser, the laser and the parametric amplifier optical communication

system are coming into vogue.

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Electronic computers have been increasingly used to

telecommunication links for processing data collection, transmission

and retrieval in private homes and in public utility services. Indeed

the future holds prospects of further advances in communication

techniques and acquires well to promote understanding and good

will among men in different parts of the world.

Telecommunication technologies have been undergoing rapid

changes all over the world and are becoming more intelligent due to

developments in electronics. Many value-added services have also

proliferated in recent years. As a result, these developments like

large-scale integration and miniaturization of components have

reduced power consumption. Also, high-density assembly

techniques have reduced the size and weight of the equipment.

Two major changes in telecommunication technology, which

have significantly influenced the telecom infrastructure, are the

introduction of Digital Signal Processing in both switching,

multiplexing and transmission of signals through fiber optic network.

The hardware technology used in switching transmission and

thermal equipment has undergone many changes since 1950 in

India. In the switching area it has changed from Strowger to Cross -

Bar in 1960, to analog electronics in 1970s, to hybrid of digital and

analog in 1980’s and now to digital electronics with higher level of

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emphasis on software based control in recent design. Similarly

transmission media on trunk routes has changed from electrical to

optical. The growing popularity of wireless transmission has resulted

in a major impact on the terminal equipment sector.

OVERVIEW COMMUNICATION SYSTEMS IN VSP:

In Visakhapatnam steel plant very wide range of communication

systems are provided for meeting the day-to-day internal an external

communication needs.

These communication needs are broadly classified as follows:

General-purpose communication systems.

Process communication systems

Monitoring and signaling systems.

General Purpose Communication Systems:

The following facilities are provided under category of

communication and signaling systems.

3000 lines electronic exchange plant.

3000 lines electronic exchange in township.

128 lines electronic exchange in township (UKKU HOUSE)

48 line electronic exchange in hill top guesthouse.

2500 line electronic exchange of Bharat Sanchar Nigam limited

in project office catering to the needs of plant area and sector-

1 to 7 in township.

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2000 line electronic exchange of Bharat Sanchar Nigam

limited in township catering the needs of sectors-8 to 11 in

township.

Process Communication System:

To facilitate coordinated operation and management of various

production shops, maintenance and service departments, the

following process communication facilitate are provided.

Dispatcher communication system.

Loudspeaker intercom system.

Loudspeaker conference system.

Industrial public address system.

Hot line communication system.

V.H.F. communication system.

Dispatcher Communication system:

Dispatcher communication systems are provided in raw

material handling plant, coke and coke chemicals departments steel

melt shop, blast furnace, sinter plant, power distribution and

thermal power plant.

These are cordless switchboard type manual exchanges of

electromechanical version meant for catering to the intrashop

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process communication needs. Since manufacture of such systems

and their spares is discontinued in the country, these dispatchers are

being placed by electronic exchanges progressively. The dispatchers

in plant control (H.O.D’s board), traffic and medium merchant

structural mill are already replaced by electronic exchanges.

Everyday teleconference is being conducted by E.D. (works) with all

H.O.D.’s in the morning with the help of digital EXCOM system

provided in the plant control.

Loud Speaker Intercom System:

Loudspeaker Intercom Systems are provided in C&CC.D., B.F.,

S.P., L.M.M.M., W.R.M. and M.M.S.M. to facilitate

intercommunication between various sections of individual plant

units on selective basis. Since the communication is carried out by

means of microphones and loudspeakers provided in the subscriber

stations, this system is very useful in noisy environment where

conventional telephones prove to be ineffective. With this system it

is possible to establish communication between any two stations

having interconnectivity on selection basis. By using group call

facility it is possible to communicate to more than one location in a

group simultaneously.

Loud Speaker broadcasting system: 18

Loud Speaker Broadcasting System is located in operation /

maintenance personal working on the shop floor as well as passing

on important process instructions to all locations in the shop area

from the concerned control rooms. The system consists of

centralized amplifier rack with amplifiers, desktop gooseneck

microphone with push to talk switch, zone selector and a network of

loud speakers connected to the amplifiers. These systems are very

useful for searching individuals on the shop floor and communicating

with them.

Loud Speaker Conference System:

These systems are provided in C&C.C.D. to facilitate two-way

communications between various sections of the shop. Since the

communication is carried out by means of microphones and

loudspeakers provided in the subscriber stations, this system is very

useful in noisy environment where conventional telephones prove to

be Ineffective. The subscriber stations are connected in a group and

it is possible to have communication with any of the two stations in

that group. The ongoing conversation will also be heard by others

connected in a group.

Industrial Public Address System:

19

Industrial Public Address System in T.P.P. is a combination of

loud speaker broadcasting and conference communication system.

From the main control room it is possible to make announcements,

which are heard at the shop floor. From certain locations the

communication can also be established through handsets in private

mode with the main control room.

Hot Line Communication System:

To ensure direct telephone communication between closely

related critical locations, direct communication systems are

provided. In this system, specified locations are connected

permanently so that whenever one subscriber lifts his telephone the

other will immediately get a ring and communication can be

achieved without any loss of time.

V.H.F. Communication System:

V.H.F. Communication systems are provided for establishing

two-way communication between operators inside the cabins of

mobile technological equipments and mobile operation /

maintenance personal with their control rooms. These sets play very

important role in C&C.C.D. for proper coordination of the

movement’s of the pusher cars, charging cars and dry quenching

20

operation coke oven batteries and C.D.C.P, areas. Hand held V.H.F.

sets are extensively used for establishing instantaneous

communications among the mobile operation/maintenance personal

with their concerned control rooms. The sets ensure instantaneous

communication and effective coordination of operating /

maintenance activities in the plant.

Monitoring And Signaling Systems:

For monitoring critical operations in different production units

continuously from the concerned control pulpits, closed circuit

television systems are provided by B.F., S.P., S.M.S., L.M.M.M.,

W.R.M. and M.M.S.M. departments. For ensuring fire safety in the

plant and to inform the central fire system immediately in case of

any fire, a central fife alarm signaling system is provided.

Closed Circuit Television Systems (CCTV):

Closed Circuit Television systems ensure supervision of critical

operating areas of major production units from their concerned

control pulpits, Each of the C.C.T.V. Systems essentially comprise

television cameras, television monitor and control console

interconnected by means of control cables and video coaxial cables.

Depending upon the requirements at the site the system may

consists of one camera and one monitor, or single camera and two

21

monitors, or four cameras and single monitor. In case of high

temperature locations the cameras are enclosed in water-cooling

and air purging arrangements. For improving the effectiveness of

cooling, vortex coolers are provided in case of furnace cameras in

L.M.M.M., W.R.M. and M.M.S.M. The cameras in B.F. are provided

with remote control pan and tilt units and remote controlled zoom

lenses for close monitoring of the cast house operations from the

control rooms. The C.C.T.V. system is provided with technical

features confirming to C.C.LR.-B standards. The C.C.T.V. systems are

provided at various plant units for observing critical operations.

Central Fire Alarm Systems:

This is provided for communicating the exact location of

outbreak of fire in any part of the steel .plant complex to the central

fire station and simultaneous actuation of sirens to alert personal of

the affected plant zone.

Communication to plant fire brigade station for exact location

of fire in any part of the plant is established either manually breaking

the front glass cover of manual fire alarm boxes which are provided

at strategic locations of various plant units all over hypertension

plant and / or automatically through voltage free contacts of plant

automatic fire detection and protection system. On receipt of alarm

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through alarm line, the corresponding signal, will start automatic

flashing on hypertension corresponding signal lamp and shall start

automatic flashing on the mimic panel provided in the fire brigade

system indicating the location of fire with simultaneous actuation of

audible alarm in the fire brigade station control room and appliance

room as well as hooting of sirens for a present time interval in the

affected alarm zone to the repeater alarm panel provided at fire

fighting and drinking water house to alert attending personal to start

fire fighting pumps immediately.

For sake of simplicity and easy identification of the fire brigade

station, the plant is divided into a number of alarm zones. To restrict

the number of alarm lines from each alarm zone, a number of

manual fire alarm boxes as well as voltage free contacts of automatic

fire detection and protection systems of shops and buildings of the

concerned zones are connected in series / parallel.

SCADA SYSTEM:

To monitor the consumption of energy by various users

in the palnt SCADA system is provided. This is placed at energy and

telecom centre. The system comprises of master station equipment

with superviousry consoles and mimic panels loaated in the energy

and telecom buliding,23 Nos remote telemetry units(RTU) installed

in different plant units and 3 local RTU’s for driving the mimic pannel

23

in the energy centre. The RTU’s will be the collecting the signsls from

the local instrumentation and electrical systems and transmitting to

the master station by means of RTU’s. the RTU’S are cionnected to

the master station by under ground telephone cables.

Shift Change Announcement System:

The shift change announcement siren system is provided for

ensuring uniform accurate shift timing through the plant. This

system consists of two numbers of quartz crystal controlled master

clocks in the energy and telecom center. The shift timings are

programmed in the master clock. At this specific time, the signal will

be transmitted for energizing the sirens located at strategic points in

plant area simultaneously at the present timings.

PRINCIPLES OF TDM-PCM:

Time-division multiplexing (TDM) is a technique used for

transmitting several analog message signals over a communication

channel by dividing the time frame into slots, ore for each message

signal. In comparison, frequency division multiplexing (FDM) divides

the available bandwidth into slots, one slot for each message signalXl

(t). The important features of TDM are illustrated in the figure :

24

25

Four input signals, all band limited to f(x) by the input filters,

are sequentially sampled at the transmitter by a rotatory switch or

commutator. The switch makes f(s) revolutions per second and

extracts one sample from each input during each revolution. The

output of the switch is a PAM waveform-containing samples of the

input signals periodically interlaced in time. The samples from

adjacent input message channels are separated by T(s)/M, where M

is the number of input channels. A set of M pulses consisting of one

sample from each of the M-input channels is called FRAME.

At the receiver, the samples from individual channels are

separated and distributed by another rotary switch called a

distributor or decommutator. The samples from each channel are

filtered to reproduce the original message signal. The rotary switches

at the transmitter and receiver are usually electronic circuits that are

carefully synchronized. Synchronizing is perhaps the most critical

aspect of TDM. There are two levels of synchronization. Frame

synchronization and sample (or word) synchronization. Frame

synchronization is necessary to establish when each group of

samples begins and word synchronization is necessary to properly

separate the samples within each frame.

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Direct PAM may transmit the interlaced sequence of samples

or the sample values may be quantized and transmitted using PCM.

Time-division multiplexed PCM is used in a variety of applications,

the most important one is PCM telephone systems where voice and

others signals are multiplexed and transmitted over a variety of

transmission media including pairs of wires, wave guides and optical

fibers.

TDM-PCM TELEPHONE SYSTEM: A 24-channel TDM multiplexer

is used as the basic system, known as the TI carrier system. Twenty-

four voice signals are sampled at a- rate of 8 KHz and the resulting

samples are quantized and converted to 7-bit PCM codewords, An

additional binary bit is added for synchronizing purposes at the end

of every group of twenty four 8bit code word another additional bit

is inserted to give frame synchronization. The overall frame size in

the ti -carrier is 193 bits and the overall bit rate is 1.544 M bits\sec.

The t1 system is designed primarily for short distance

and heavy uses in metropolitan areas. The maximum length of the tl

system is now limited to 50 to 100 miles with a repeater spacing of 1

mile. The overall T-carrier system is made up of various combination

of lower order T carrier subsystems designed for accommodating

voice channels, Picture phone service, TV signals, and (direct) digital

27

data from data terminal equipment, In additional to using metallic

cable systems for transmission, optical fibers with repeaters have

been used to transmit binary data at speeds of 1.5, 3.6, 45 and 274

Mbits/sec corresponding to the speeds of the digital transmission

hierarchy.

BASIC TELEPHONE INSTRUMENT

INTRODUCTION:

The basic telephone circuit is architecture around three ICs

chipset consisting of dialing block- realized by using IC, ringer block-

realized through IC and speech block-realized through IC.

The telephone circuit consists of the following functional blocks:

Ringer circuit.

Current limiter circuit.

Dialer circuit.

Speech circuit.

Protection circuit and

Special features.

RINGER CIRCUIT:

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The ringer circuit is built around the tone ringer IC and a few

discrete components. This part of the circuit has a low current

consumption to allow the ringer performance. The ringer IC has built

in bridge rectifier with zener diodes to protect against over voltages.

The IC generates pleasing tone composed of a high frequency

alternating with a low frequency resulting in a variable frequency.

The output of IC directly drives the ring.

The DC voltage required for operation of the IC is generated

from the ring AC signal. The ring signal, which is fed to the IC via the

capacitor C4 and resistor R41. The supply voltage is filtered through

capacitor C43. The current is limited by resistor R41 thus limiting

power dissipation in the IC.

The tone frequency is determined by the external resistor R42

(1 5 K) and capacitor C42 (O.OluF) volume of ringer is controlled by

potentiometer R43 (l00 KQPOT).

CURRENT LIMITER CIRCUIT:

Current limiter circuit is connected in series with the line at

nodes ‘A’ and ‘B’. in a standard model this is implemented through

two resistors placed R55(68Q) and R56(47Q). In this case short line

current will be between 75 to 80mA.

DAILER CIRCUIT:

29

The dialing circuit is built around the tone/pulse switchable IC

UM9/2/4B and few associated components. Internal timings of the

IC are derived via crystal (xl) of 3.58MHz crystal, ceramic resonator.

It provides dialing pulse and Dual Tone Multi Frequency (DTMF).

The IC is provided by the supply from Vcc through diode D5.

This diode prevents discharge of capacitor C22. During on hook,

zener diode Z21 limits the supply voltage to safe operating region of

the dialer IC. During on hook, IC is powered through diode bridge

DlOl-D104 and R21. The hook condition of the handset is detected by

HK input (pin 1). Off hook provides bias to base Q2l through R29 and

R30. Q21 conducts and pulls HK to low.The IC derives its timings

from 3.58MHz Quartz crystal or resonator connected to pins 3 and 4.

The row outputs and column inputs are connected to the keyboard.

The default-dialing mode selected through mode - in (pin 2) via

mode switch p/t. if mode - in pin is grounded through this switch

tone mode will be activated and if connected to Vdd, pulse mode is

activated. In pulse mode,”*h’ key used to switch dial mode to tone

mode from pulse.

In normal state, DP (pin 11) and mute (pin 8) are in high state.

When a key is pressed, the mute pin changes to “low” state. This

makes mute input of IC(PIN 12)”LOW” and in turn it mutes the

receiver and transmitter amplifiers.

30

The dial pulses are transmitted from DP(pin). Normally

transistor Q25 is off which puts transistor Q24 on. Conduction of Q24

put transistors Q22 and Q23 in conducting mode thus, circuit,

drawing current from the line. During pulses on/off interrupting loop

current for pulse break time and making loop during pulse make

time. Number of pulses transferred on line depends on the key

number dialed. At the end of pulses the mute output is switched to

“high” so that the speech circuit is connected again. Make/break

ratio is set to 33.3 to 66.6 ms. Dial rate is 10 pulses per second.

In tone mode the frequencies according to CCITT are derived

from a crystal oscillator XI. In this mode when a key is pressed, the

DTMF tones are generated at pin 7. These tones are fed via pre

scalar network R26, R27, C21 and C24 to speech (pin 11). The DTMF

signal is set on the line after amplification by IC. Dialer generates low

mute signal during which turns OFF transmit and receive amplifier, it

is possible to hear DTMF signal as a confidence tone receiver.

The optional REDIAL key facilitates 12-digit redial in pulse mode

and 31 digits redial in DTMF mode.

SPEECH CIRCUIT:

Speech circuit is based on low power and low voltage IC . The

power to the IC and its peripheral circuits are obtained from the line.

Depending of supply pin (no.13) is by capacitors C3 and C4. The

31

internal voltage regulator is decoupled by a capacitor C6. The circuit

has an internal current stabilizer where operating level is determined

by the line current and resistor R8. The regulated voltage on the line

(pin 1) is determined by the line current and resistor R4. The circuit

has symmetrical microphone inputs (pin 7 MIC +and pin 6 MIQ.

Electrets microphone is used in the circuit. The microphone gain is

controlled by resistor RIO and set at about 48dB. Stability is ensured

by capacitors C13 and C5. The cut off frequency is determined by

time constant of RIO and CS.

The receiving amplifier has one input (pin 10) and a non-

inverting output (pin 4). Dynamic type earpiece incorporated in the

circuit. The receiving input fed to circuit via resistor rl and capacitor

C12 from the line. The gain of receiver is controlled by resistor R7

and set at about 37dB. Two external capacitors C7 and C8 ensure

stability of receiving amplifier. The cutoff frequency will depend on

the time constant R7 and C7.

Automatic line compensation is achieved through resistor R9.

The automatic gain controller varies the gain of the microphone and

the receiving amplifiers in accordance with the DC line current. The

controlled range is 5.8dB, which corresponds to a line of 5KM for a

0.5mm diameter twisted pair copper cable.

32

The anti side tone network consists of R2, Rll and Z BAL (i.e., R3

+ R13// C14). Suppresses the transmitted signal in the earpiece. The

anti side tone network in the circuit attenuates the signal received

from the line by 32 db before it enters the receiving amplifier. The

attenuation is almost constant over the whole of audio frequency

range.

PROTECTION CIRCUIT/COMPONENTS: The design incorporates

two levels of protection in the circuit. Level 1 protection is against

surge voltages. The level 2 protection is meant to handle high

voltages and protect the speech and dialer IC’s.

VARISTOR VDR1

VDR is used across the line terminals to protect the equipment from

surges that may occur or induce on telephone lines. This device

discharges over voltage to other line (up to 2KV with a pulse of

10/700 us) and protects the remaining circuit from damage. During

lightening or switching relays at exchange may generate high

voltages on telephone line, which may cause damage to telephone.

These high voltages are clipped and surge currents are by passed to

other wire by VDR.

DC OVER VOLTAGE PROTECTION:

33

The level 2 protection against the DC voltages will prevent damages

that might happen to speech and dialer IC’s and other parts of the

circuit elements. The Z1, Z22 and Z21 perform the functions by

limiting the DC voltages to the safe operating voltage limits of the

circuit elements.

OTHER SPECIAL FEATURES:

REDIAL:

The dialer IC has a last number redial memory register. The last

number dialed through telephone will be stored into the register.

This feature will be available in both modes of dialing. The feature is

activated through’ Redial’ key.

THE 3000 LINES PLANT TELEPHONE EXCHANGE

INTRODUCTION:

Earlier in the plant telephone exchange of NE 1300 model of

OKI technology was in use. This was replaced by the present

exchange on 1st September, 2010. This exchange is of ALCATEL -

LUCENT technology of France. This ALCATEL-LUCENT exchange is

designed initially for 3000 subscriber and is capable of expanding up

to 10,000 lines at later by adding required hardware and license to

34

the server . The exchange is provide with 120 PRI- junctions for

interacting with the 3000 line electronic exchange.The Exchange can

act as local and transit exchange to facilitate interconnection of the

above Exchanges. The exchange is also provided with 500 hot lines,

500 analog long lines, 48 digital lines etc.

PLANT TELEPHONE EXCHANGE

HIGHLIGHTS : MAKE : ALCATEL-LUCENT

MODEL : Omni PCX Enterprise Communication Server

CAPACITY : 10,000 Lines

CONFIGURATION :

ANALOG SUBSCRIBER LINES : 3000 (1200 ohms)

DIGITAL LINES : 48

ANALOG LONG LINES : 500 (3000 ohms)

LD TRUNK LINES : 60

35

HOT LINES : 500

BRI- TRUNKS : 8

IP EXTENSIONS : 100

CO TRUNK LINES : 30

PRI CHANNELS : 480

IP TRUNKS : 100

And with software licensing upto 5000 ports.

INTERCONNECTION DIAGRAM OF EXCHANGE

156 LD TIE

120 PRI (FIBER) JNS LINES

AND 100 IP CHANNELS 120 PRI Jns

60 PRI Jns

60 LD TIE LINES

30 PRI Jns

150 PRI Jns

36

3000 LINES SIMENS ECHANGE

IN TOWNSHIP

PROPOSED 3000 LINES

EXCHANGE IN

3000 LINES OKI EXCHANGE IN

PLANT

PSTN EXCHANGE

IP EXCHANGE AT ADMIN

BLDG

PLANT TELEPHONE SYSTEM (PTS) FOR 6.3MT EXPANSION

FACILITES AND FEATURES OF THE EXCHANGE ARE:

REMOTE MAINTENACE INTERFACE LAN – CONNECTIVITY

IVRS FOR AUTOMATIC COMPLAINTS HANDLING SYSTEM

CALL BILLING SYSTEM

BUDGETING SYSTEM

UNIVERSAL SLOTS

CPU7-2 PROCESSOR

AUTO CALL BACK ON BUSY / NO ANSWER

WAKE-UP / REMINDER ALARM

CALL PICK-UP (INDIVIDUAL OR GROUP)

DO NOT DISTURB

CALL FORWARD ON NO ANSWER AND ON BUSY

CALL TRANSFER

3- PARTY CONFERENCE

6-PARTY CONFERENCE

37

CALL WAITING

CALL PARK AND RETRIVE

INTRUDE

PAGING

CALL TRACING

MUSIC ON HOLD

VOICE GUIDANCE

MSG IN THE PLACE OF DAIL TONE

TIME ANNOUNCEMENT IN THREE LANGUAGES

IP COMPATIBLE

OFC COMPATIBLE

E1 COMPATIBLE

EXPLANATION ON FEATURES :

1. Three Parry Conferences:

While in conversion with another subscriber, if the first subscriber

dials a code Number of the third subscriber then all the three can

have a conference together.

2. Auto call Back on Busy/No answer:

When a subscriber gets an engage tone after dialing a number, he

need not dial all the numbers again. Instead, he can just dial a code

38

and put back the receiver in the normal position. As soon as both the

numbers are free, ring will be sent to both the parties and the

speech between them can be proceeded.

3. Wake Up Service Facility:

A local subscriber can set up alarm for the required time just by

dialing a two digit code and the required time at which he requires

the alarm.

4. Call pick up: This facility enables a subscriber A to pick up the call

of subscriber B if he knows that the instrument of B is in ringing

state. This facility is availed by subscriber A by dialing a two digit

number of subscriber B, while instrument of subscriber B will be in

the ringing state. If the subscriber avails this facility, the instrument

of subscriber B will be terminated from ringing state thus

transferring the call to subscriber A.

5. Do Not Disturb:

This facility is exercised by dialing a two- digit code. After exercising

this facility any subscriber who dials this number will get busy tone,

till the subscriber exercising this facility redials a two- digit

cancellation code.

6.Call Forward:

This facility enables a subscriber to forward all his calls to another

local subscriber, for example, subscriber A can dial a two-digit code

39

and the telephone number of subscriber B who is a local subscriber.

Now all the calls of subscriber A will go to subscriber B. unless and

until subscriber A canals his call forward facility by dialing a two-digit

code.

7. Call Transfer:

While in conversation, if the subscriber wants to transfer the call to a

third subscriber, he can dial, a code and telephone number of the

third subscriber and after getting him, replace the receiver.

8. Call Billing System:

All the out going calls are origination can be recorded into a PC with

the help of this system. By using a software called IIESCAPE** the

call billing PC records a) All the origination call numbers b) lime of

origination c) Duration of call.

This system is provided to prepare the call billing extension wise for

all the call originations within the exchange. A dedicated PC is

assigned for this system to monitor all the out going calls. Malicious

calls can be traced with the help of this system.

9.Interactive Voice Response System:

By dialing a code (174) the time is announced by this system and also

by dialing 198, telephone complaints can be logged with the help of

40

a voice prompt. All these complaints will be stored in a database in

the PC which dedicatedly assigned for this system.

BASIC BLOCK DIAGRAM OF POWER PLANT AND TOWNSHIP EXCHANGES:

41

DC SWITCHING

CUBICLE

SWITCH MODE RECTIFIER-UNIT-1

VRLA -BATTERY BANK -I

ADMIN &MAINTENANCE-

CONSOLE

SWITCH MODE RECTIFIER-UNIT-2

VRLA -BATTERY BANK -2

48 V DC VOLTAGE

30-E1-Channel (I/C)

440 volts

3 phase incoming power supply

As shown in the figure, the Township and plant Exchange equipment

mainly consists of the following equipment :

1. AC Incomer unit 2. Power Supply

DC Power supply Battery

3.Switching equipment4.MAC Consoles

5.MDF equipment

AC Incomer unit :

42

SWITCH

MAIN DISTRIBUTION FRAME

3000 LINES TO FIELD SIDE

The Exchange is provided with 440V Ac, 3-ph

power supply through two different feeders one from MRS (APSEB)

and other one from TPP direct. These feeders are swappable

whenever required depending upon the power availability. Incoming

power to Power plant is supplied through these feeders and through

a lever switch mechanism for each of the two SMPS units separately.

POWER SUPPLY:

Each cabinet requires either a 220V or 110V AC

electrical power supply or a 48V electrical power supply. The racks

are delivered without batteries so whatever type of power supply is

required should be equipped with an external battery solution.

To allow the equipment to operate autonomously during

prolonged power failure different power back up solutions are

offered.

An appropriate external uninterruptable power supply

(UPS) can be used. The UPS is directly connected to

electrical power outlet at base of rack. This solution

operates with 110V/230V rack module.

43

An external battery solution either in desktop format or

in a rack format can be used.

Two voltages are provided: 12V for 1-rack module and

36V for 3-rack module. This solution operates with

110V/230V rack module.

DC Power Supply Equipment: The power supply unit basically

converts the available AC power (440 V AC, 3-phase) into 48 V DC. AC

power is given to the SMPS rectifier units through a switch and a

fuse cut – out assembly.

The Power Supply Equipment consists of:

2 no of Switch Mode rectifier units that is SMPS based

Power supply units designated as SMP-1 & SMP-2. Each unit is

having a CSU and six rectifier modules of 50 Amps capacity each,

connected in parallel. The CSU has a display unit which displays the

various parameters like Voltages , Currents , Alarms and battery

status etc., The exchange normally draws a load current of 50 Amps

approximately.

1 no of 600 Amps Manual DC switching Cubicle unit

consisting of knife-switch arrangement is provided to SMPS power

plants and battery banks. Provision is there to connect / disconnect

44

SMP1, SMP2, Battery bank-1 & Battery bank-2 using simple knife

edge switches in any combination. The Load terminal of the supplied

Manual Switching Cubicle unit is permanently connected to the

exchange load. In the event of mains power failure the Exchange will

be automatically connected to battery supply without any

interruption.

2 no of VRLA Battery Banks each 1000 Ah capacity are

connected in float with the load.

The electrode reactions in all lead acid batteries are

basically identical. As the battery discharges, the lead dioxide

(positive active material) and the spongy lead (negative active

material) both react with the sulphuric acid (electrolyte) to form lead

sulphate and water. During charge, this process is reversed.

In conventional lead acid batteries towards the end of

charging, oxygen gas is evolved at the positive electrode and

hydrogen gas is evolved at the negative electrode. These gases then

make their way out as bubbles through the electrolyte and escape

into the environment; thereby water is lost from the battery.

Therefore, periodic topping up of these batteries with demineralized

water is required.

45

In VRLA batteries, the oxygen generated at the positive

plate is transported in the gaseous phase through the micro porous

Absorbent Glass Mat (AGM) separator to the surface of the negative

plate. Here the oxygen gets reduced by reacting with the charged

active material i.e., the spongy lead of the negative plate; thereby

the formation of hydrogen gas is effectively suppressed.

Consequently, the VRLA battery does not lose any water and

therefore, no topping up is required. This is also known as the

Oxygen Recombination Process. These batteries come with self-

resealing valves that release excess gases into the atmosphere in the

event of overcharging. Therefore, complete safety is ensured, hence

the name – Valve Regulated Lead Acid batteries.

Charging considerations:

For optimum battery life, the charging equipment

should posses the following features:

A constant voltage charging mode with current limiting

features

Float voltage: 46 to 56 V

Boost voltage: 50 to 61V

The maximum battery charging current is to be limited to

20% of the rated capacity

46

Over voltage cut-off: 2.33 VPC

Under voltage cut-off: 1.75 VPC

Voltage regulation: ±1%

Voltage ripple <2% of the RMS value

Current ripple< 5% of the RMS value

Auto float to boost changeover facility at:

a. Float to Boost : 5% of the rated Ah capacity in

Amps

b. Boost to Float : 3% of the rated Ah capacity in

Amps

Operation:

The VRLA batteries have to be charged only in constant

potential current limiting mode. The charging current is to be limited

to a maximum of 20% of the Ah capacity of the battery. Recharging is

to be done immediately after a discharge. A logbook should be

maintained for recording all discharges. Further the charger/power

plant should be compatible for charging. Charge voltage settings

should be as follows:

Recommended voltage settings:

47

Mode 15-32ºC Above 32ºC Current Limit Set

(Amps)

For 24

cells

Single

cell

24

cells

Single

cellMin. 10% - Max. 20%

of

Battery Ah Capacity

Float 54.0 V 2.25 V 53.5 V 2.23V

Boost 55.2 V 2.30 V 54.7V 2.28V

Note: a) Unless otherwise stated, limit charge current to 20% of

rated capacity of the battery.

b) Maximum voltage ripple content permitted < 2% RMS.

System Monitoring:

General:

VRLA batteries are maintenance-free, provided they are used

and monitored as per instructions. These batteries do not require

the addition of DM water/acid or regular specific gravity checks. The

battery should be monitored regularly for obtaining optimum

performance4 throughout its operating life. A complete recorded

history of the battery operation would be helpful in doing this. Good

48

records will also help when corrective action is required to eliminate

maintenance problems.

Monitoring:

An IEEE standard 1188-1996 recommends certain

maintenance and monitoring procedures for VRLA batteries in

stationary applications. The following monitoring instructions are

used for VRLA batteries in line with the recommended IEEE standard.

To ensure optimum performance the batteries need to be

inspected/monitored at periodic intervals. This will also help to

identify any weak cell in battery bank, so that corrective action can

be initiated. The following steps are to be followed to extract the

optimum performance from the VRLA batteries.

SWITCHING EQUIPMENT:

Switching equipment is the heart of any telephone

exchange, the plant exchange switching equipment is housed in 4

cabinets that are consists of

– CONTROL SHELF

– PERIPHERAL SHELF

49

The CONTROL SHELF consists of all the control cards, Hard disk

drive, and interface cards units for peripheral shelves.

The PERIPHERAL SHELF consists of all the line cards , trunk

cards , and interface cards with the control shelf .

All the cabinets are fed with individual –48 V, DC supply

from the bus bars . The –48 V supply is wired to all the sub racks in

the cabinets internally on the back panel mother board. Also earth

connectivity is extended to all the cabinets from the earth pit.

CALL PROCESSING:

The total call processing or communication between any two

subscribers is basically divided into two parts:

a) Signaling

b) Speech transfer

Signaling part:

50

The processor continuously monitors all the lines for any loop

in pre-determined time intervals (milli seconds). The various

sequence operations that takes place during signaling are:

When any of the subscribers lifts his telephone hand set, the

loop will be detected by the exchange and the dial tone will

be switched.

Processor collects the digits dialed by the subscriber.

Digit analysis(1st digit) will be done by the processor so as to

route the subscriber to his destination number

If the destination number is busy or off-hook the processor

switches the busy / engage tone to the originator number

Ringing current will be passed to the destination number

Ring back tone will be switched to the originator number

Processor continuously monitors the destination for his

response to the ring

Once the destination party lifts the receiver the processor

has to cut-off the ringing current as well as the ring back tone.

All these above mentioned activities are part of the call

processing and come under signaling part of the call processing.

Speech part:

51

The subscriber line card ez32 consists of 32ports / circuits

Each port is for one telephone number.

The various sequence operations that takes place during

speech part are:

The analog electrical voice signals from the telephone hand

set transmitter of the originator number / destination

number reaches the ez32 card in the switch.

The analog speech signals are then converted into digital

form by using A/D converters.

Digital speech signals are sampled by Pulse Code Modulation

(PCM) coding

The PCM coded speech information is further sampled.

Sampled speech signals are Time division multiplexed (TDM)

From the available TDM signals the processor identifies the

originations address and destination’s address, then

switches A’s speech to the B’s circuit and vice versa.

The TDM signals in the respective circuitry are

demultiplexed, PCM decoded, converted from digital to

analog form.

The analog speech signals of originator / destination are

transferred to their receiver circuits

52

Thus the communication takes place between the

calling party and the called party.

DIFFERENT TYPES OF CARDS USED AND THEIR FUNCTIONS:

CARD NAME FUNCTION

EZ32 Analog extension card-

32 port

EAU32 Digital extension card

INTOF2A Pheripheral act shelf

interface

NDDI2-2 CO-Trunk board-8 port

INT-IP2 IP Interface for IP

Trunks & IP Lines

LDTL-8 Analog Trunk-8 port

INTOF-2B Pheripheral act shelf

interface

NPRAE-2 PRI Trunk Bord-2X30

CPU 7-2 Main Processor

53

LTU-1LTU-2LTU-12LTU-15

FUNCTIONAL DESCRIPTION OF CARDS USED :

CPU-7-2:

The CPU-7-2 processor unit is the heart of the system it handles system applications(telephone applications, telematic applications ,voice mail applications etc).

The CPU-7-2 board is built around a altra low power Celeron running at 650 MHZ. the board has up to 256MB of SDRA.

INTERFACE BOARD CONTROL:

The CPU-7-2 board controls the interface board. It ensures the following functions.

Downloading.

Synchronization clocks.

Start up and reset commands.

Auto attendant.

HARD WARE:

The CPU board allows the connections of either

A 2.5 inch IDE hard drive. This hard drive is installed on the CPU-7-2 board.

A SATA hard drive. This hard drive is installed on a P SATA 4K card fixed on the CPU-7-2 board.

ETHER NET CONNECTIONS:

54

The CPU-7-2 board has :

A half or full duplex 10/100 base t-interface for connection to the outside world this interface can be configured using the ethctl to

An embedded 10 bits per Ethernet interface intended for traffic between ACT boards and CPU re between the 2 CPUS

SOFTWRE PROTECTION:

On the CPU-7-2 the software protection mechanism operates with the cpu identifier.

CPU REDUNDANCY:

The CPU-7-2 may be duplicated for enhanced operating safety for this configuration both CPU’S must be running the same software version.

The remote CPU and its role are detected by software as well as by the backplane clock signal ( for the stand-by position).

EXTERNAL MUSIC:

The CPU7-2 has an input music-on-hold .The analog signal from the recorder is digitized accordind to the A la or mu la depending on the configuration used

TONES:

55

The CPU-7-2 board has ten Q23 or Q23 type tone detectors. Selection of Q23 or Q23X sensitivity is performed by the software.

The CPU-7-2 board has tone generators.

LEDs:

The CPU-7-2 board has 2 LEDs on the front panel

green LED: CPU status indicator

orange LED: Ethernet 10/100 base t connection activity indicator

POWER SUPPLY:

The CPU7-2 board runs on a 48v DC power supply. When the CPU7-2 board recevies the PSAL signal,a procedure is initiated to allow a correct system shut down.

The PSAL(power supply alarm)signal is generated by the PSAL board that monitors power supply voltage.When power supply voltage falls below 45v,the PSAL signal is set.The cpu then shut down.

NPRAE BOARD:

The NPRAE is New Primary Rate Access E1 board.

This board can be used to connect an Alcatel-Lucent OmniPCX Enterprise CS to:

Another Alcatel-Lucent Omn iPCX Enterprise CS in a private network.(ABC-F,Q-SIG)

56

A Non Alcatel PBX in a private network(DPNSS)

A Public network.(ISDN,DASS2)

The NPRAE board can provide EVEN E1-(T2)access.

Note: clock synchronization can be obtained from the board access if needed to synchronize node.

FUNCTION UNITS:

The NPRAE board is composed of the following functional units:

One Switching Module.

To ISDN E1 Interfaces i.e using this board we can connect on PRI line on single board.

NDDI2-2 Board:

It is an analog board which allows the Private Automatic Branch Exchange (PABX) to be connected to most public networks. Furthermore, this board allows the PABX to be connected to a pager system according ESPA standard. The NDDI2-2 board can connect up to eight 2-wire analog lines.

The NDDI2-2 board is made up of the following funtional blocks:

Analog Interfaces.

Digital signal processing(DSP)module.

Power Supply.

57

ANALOG INTERFACES:

Control the signaling.

Transmit voice

Interfaces are made up of the following parts:

Protection circuits:

Overvoltage protection circuits to avoid damage in case of any short circuit.

EMI filtering circuits to reduce the RFI effects on the telephone line card.

Impedance for signaling:

A firmware command allows a low or high impedance to be connected.

LOOP CIRCUITS:

Online loop

Dialing loop(very low resistance)

Loop current detector

DSP MODULE:

TONE DETECTION:

Eight channels are available for tone detection.

External Tone Detection: There are two types of tone

Dial Tone

58

Busy Tone

Ringing Detection:

Eight detection necessary on the NDD12-2 board . The detector must be handled frequencies ranging from 14.52 to 68 HZ.

TAMIS terminal equipment alert signaling(TAS) detection:

Eight TAS detection channels are necessary on the N DD I2-2 board.

The TAS can be:

Dual tone alert signaling(DT-AS)

Ringing pulse alert signallingI(RP-AS)

Frequency shift keying(FSK) demodulation:

8 FSK demodulation channels are necessary on the NDDI2-2 board(8 FSK carrier detections are provided).

Dual tone multi frequency(DTMF) detection:

COMMON PART:

The common part is a interface between the NDDI2-2 board and the other ACT boards. the revision card NO (RCN) register of the QLSLAC recognizes the NDDI2-2 board

The MIC zero link rated at 2.048MHz transmits voice for 8 NDDI2-2 lines.

POWER SUPPLY:

59

For -48V power supply, the CM 8 convertor supplies the NDDI-2 board with +5V,-5V and +12V.

3.3V regulator supplies the QLSLAC and DSP module.

EZ32:

The EZ32 board is an analog subscriber line. This board gives 32 analog ports. Subscriber line cards are designed to interface the analog subscriber line to a PCM highway in a digital central office or a Digital Loop Carrier(DLC) .Subscriber line interface module(SLIM)devices are complete electronic subscriber line interface circuit(SLIC).

Line cards typically interfaces the twisted pair cable of a POTS local loop to the PSTN .Telephone line cards perform multiple tasks ,such as analog to digital and digital to analog conversation of voice, off-hook detection .In telephone exchange designs, the line cards generate ringing current and decode DTMF signals.

EZ32 consists of following units:

One out put stage for EMC filtering and over voltage protection.

8 QCIALAs, each comprising:

-1 COFIDEC ( analog signal encoder / decoder with built in filtering ).

-4 CIALAs.

1 common C1NV part.

2 CBI and CB26 power supply convertors

60

OUT PUT SATGE:

For each line, the output stage ensures:

Over voltage protection.

Common mode interfacing filtering.

LONG DISTANCE QCIALA (QUADRIPPLE SUBSCRIBER LINE ANALOG INTERFACE CIRCUIT):

This daughter board has an analog interface line and ringing injected circuit. Each CIALA handles an analog termination.

The interface ensures the 48V supplty of the line and current regulation. It performs the 2to 4 wire switch over.

By monitoring the line it generates signallling( off hook, consultation call) and sense this signaling to the C1 MB via OET links across the PCM interface.

The ringing injected circuit, validated by the ringing command, amplifies the ringing strem. The call flow is sent on the line

COFIDEC (SUBSCRIBER LINE ANALOG I BTERFACE CIRCUIT):

This component converts the analog voice signal into a digital signal and vice versa. It handles four channels simultaneously. To handle the 32 terminations a COFIDEC is installed on each of the 8 QCIALAs. On receiving an order from the CPU, the COFIDEC decodes the ringing byte into a analog for the ringing injector.

COMMON C1NV PATH:

61

The common path interfaces the Z32 board with other system board.

The main parts are:

A C1 like unit, which ensures;

Switching

Generation of the clock signals

Signaling for CPU and line busy state

Tone generation

A CPU comprising:

An ARN microprocessor running at 32.7768MHz

A flash Eprom ( external to C1NV).

A DSP( digital signal processor) for DTMF ( internal Q23 or external Q23X) signal detection and digital processing.

Input out ports.

Generates the following clock signals.

8 KHZs for frame synchronization.

2.048 MHZs for the QCIALA interface.

2*512 KHZs per synchronization of the CB8 and CB26 power supplies.

EUA32:

62

The EUA32 card is a digital extension card. This board 32 digital ports.

FUNCTIONAL UNITS:

The board consists of the following different units:

Four UA modules.

1 common C1 NV port.

1 CB8 power supply convertor.

NOTE:

UA modules provides a interface between the UA and PCM link for the board.

UA QUAD LINE TRANSFORMERS:

Each quad transformer converts the 0V/3.3V signal into a -2.5V/2.5V signal, that is sent on the UA line.

Two UA quad line transformers connected on a PCM link each quad handles 4 UA lines.

INTOF2:

The INTOF2 board can be used for the connection of a peripheral ACT shelf through a specific link

INTOF Behaviour:

TwoINTIF2 boards are used to connect two ACT shelves via an INTOF link.The board in the higher level ACT is called INTOF2A while

63

associated board is called INTOF2B nad must be plugged in a CPU slot.

AN INTOF2 CONNECTION CAN BE:

A copper link. For short connections a satnadard alcatel cabel may be used. For distance( <5m), twisted pairs are required.

A monomode or multimode optical fibder link. In this case an external COST board is required.

INT IP2:

The INT IP2 board acts as an IP interface with the compressor channels on daughter board on it. The same can use for ip communication over protocols such as H323 and SIP.

PROCESSING UNIT: This includes the following parts:

Micro processor

1 dynamic 32MB SDRAM working memory.

1 dynamic 16MB communication memory (not installed)

2MB flash EPROM for the boost.

SWITCHING UNIT:

This unit is made up of:

One programmable logic module

64

This module interfaces the processor and the input/output common port containing the C1 component and the Vivalid chip.

DAUGHTER BOARD INTERFACE:

This unit ensures the interface between the processor and the DSP speech compression modules located on the daughter boards.

It handles a maximum of two daughter boards and 56 compressed channels with the GIP6, or 60 compressed channels with GIP4.

The compressor channels can be used to integrate the application like internal and external conference devices over IP.

POWER SUPPLY:

The convertor supplies +3.3v , +5v , and +2.5 v (INT-IP) or +1.5v (INT-IP2) voltages from -48 v powering the board.

GPA2 :

The GPA2 board is general purpose auxilary2. The GPA2 supports two main applications:

Voice (speech) processing:

Multi language voice guides (multi language voice prompt), that can be downloaded in a maximum of 4 languages and that can be simultaneously broad cast on 60 channels.

4*6 MB (4*12 min) static voice guides.

65

7.5 MB (15 min) dynamic voice guides.

Music –on –hold.

Processing of the tones and DTMF frequencies used on the different public or private networks.

Generation of tones , Q23, Q23X, DTO(CCD) 2100Hz.

R1/R2, VAD.

Three simultaneous conferences can be set up,each with30 participants.

FUNCTIONAL UNITS:

The GPA2 board consists of the following units:

The switching unit, based on the common C1NV part, to interface board with other system boards.The signaling processing unit, based on the two modules each compressing a DSP and an SDROM memory:

The DSP zero and its assosiciated 32Mb SDRAM memory are dedicated to the multi language voice prompt features.

DSP1 and its associated 8Mb SDRAM memory or dedicated to N party conference feature

The power supply provides DC voltages of 1.18v,3.3v and 5v via to dc/dc converters

Note: A back up battery allows voice guides to be saved when the GPA2 board is unplugged (several hours autonomy)

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GENERAL FAULTS – DIAGNOSIS IN THE

EXCHANGE

Fault / Symptom Check DIAGNOSIS

No Dial tone

complaint

Check the DT at the

MDF …. if YES

Fault may be in the

IPM/jumper/field

MDF

If NO If the DT is there in

the previous

number and next

number, ez32 card

may be faulty.

Replace the card.

Township numbers

not getting /

Township junctions

not working

Check the NPRAE-2

cards LED status. If

they are blinking

continuously..

Fault in junction

lines.

Plug out and plug in

the TMLR2 cards

ZERO – dialing not

working

Check the BSNL dial

tones at the krone

MDF

Replace the TM2LP

card

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( 30 numbers ) If

YES

If NO To be informed to

the BSNL exchange

MAC CONSOLES:

FOR MAN MACHINE INTERFACE:

The Exchange can be programmed from a Personnel computer

(PC) which is connected to it by a serial port / a LAN port via RMA

box through telnet/RS232.The interaction is of command prompt

type. The maintenance can also be done through a software is called

“NMC-4760“which runs in Windows Operating system environment.

and is a graphical user interface (GUI) based. By using RMA box or

“NMC-4760“application on the MMC PC programming and diagnosis

is being done.

FOR CALL BILLING:

All the out going calls or originations can be recorded into a PC

with the help of this system. By using a software called “CUBE”, the

call billing PC records

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All the originations call numbers

Time of origination

Duration of the call.

This system is provided to prepare the call billing extension

wise for all the call originations within the exchange. A dedicated PC

is assigned for this system to monitor all the outgoing calls. Malicious

calls can be traced with the help of this system.

FOR IVRS (INTERACTIVE VOICE RESPONSE SYSTEM):

By dialing a code (174) the time is announced by this system

and also by dialing 198, telephone complaints can be lodged with the

help of a voice prompt. All these complaints will be stored in a

database in the PC which dedicatedly assigned for this system.

MDF – EQUIPMENT:

MDF stands for Main Distribution Frame where all the

subscriber lines and junction lines from the Exchange are terminated

on one side and field cables on other side. This facilitates the

jumpering of any number to any location as per requirement and

also to isolate Exchange side from the lie side to identity the fault. It

provides protection to exchange by employing PTC and GD tubes.

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PTC is Potential Temperature Coefficient i.e., it has a varistor where

its resistance increases and opens beyond certain current in order to

protect the subscriber card from drawing excess current. GD tube is

a gas discharge tube (pin 3 ), which is kept across A to earth and B to

earth. This protects the exchange against high voltages due to

lightning. HT induction, foreign potential etc., by the action of gas

ionization in GD tube beyond 100V AC / DC and grounds the external

voltage.

The Exchange side of MDF consists of six columns of hundred

pair module blocks each. There are six rows per column providing

3,500 cable pair terminals. Each hundred pair module consists of 10

numbers of ten pair disconnection modules. The subscriber lines,

trunks are terminated in module blocks from B1 to B33.

The line side of MDF consists of twelve columns of hundred

pair module blocks each. There are six rows per column catering to

7200 cable pair terminals. Each hundred pair module consists of 10

numbers of ten pair disconnection modules. All the line side cables

are terminated in the blocks numbered from Ml to M72.

Automatic Line Testing Equipment (ALTE):

The MDF is provided with Automatic Line Testing Equipment

(ALTE). It is a PC based system through which the testing of the

subscriber is done.

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The following tests can be performed with the help of ALTE.

Foreign potential (AC / DC) in limb A.

Foreign potential (AC / DC) in limb B.

Insulation resistances of limb A with respect to earth.

Insulation resistances of limb B with respect to earth.

Insulation resistances between limb A and limb B.

Capacitance.

The measured values are compared with the already initialized

values in the database and the line is declared as pass or fail.

Provision is also provided to test,

A single line.

Sequentially on group of lines.

Sequentially on number of line groups.

Sequentially on all lines.

Or selection of required test is also possible.

The MDF is main distribution frame where the cables from

the field side and the exchange side are terminated. In township

exchange MDF is being used to terminate all the exchange cables. All

the dial tones from the exchange are available in the MDF which is

provided with IPM s so as to protect the exchange equipment from

the external high currents and voltages. The dial tones are extended

to the field side MDF via IPMs and jumper wires .Similarly all the

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trunk circuits are available in the MDF and these trunks are further

connected to PLEX trunks / BSNL trunks in the MDF.

Main Distribution Frame (MDF) is of four thousand (4000)

port capacity and equipped with 40 no of 100 pair CT blocks with 11

way back mount frame and 2/10 disconnection modules mounted on

a painted, prefabricated steel structured frame and seamless

interface for terminating exchange cables & field cables, provided

with hooks & rings for jumpers, with Integrated Protection Modules

(IPM)s which consists of PTCs and Gas Discharge Tubes for all the

ports (Lines, Trunks) of KRONE-make.

The MDF is provided with cable connections in the rear,

channels for running the cables, twin insulation Displacement type

contacts, test plugs, front access to jumper connection tags/ferrules,

replaceable contacts ,rubber floor mat covering entire MDF area etc.

OTHER GENERAL OBSERVATIONS TO BE MADE :

At the beginning of the shift the Power supply readings in

the CSU –display are to be noted.

Check for any alarms in the Power supply unit

Check the Major/Minor alarms in the Exchange

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Check the temperature in the exchange thermo meter

and accordingly the no of compressors are to be switched

ON in the AC plant.

FEATURES IN PLANT EXCHANGE

90 WAKE UP SERVICE CANCELLATION 91 WAKE UP SERVICE REGISTRATION (91 Followed by Time in 24 hrs mode)

92 CALL PICK UP (92 Followed by telephone number)

93 DO NOT DISTURB ( Not activated ) 95 DO NOT DISTURB CANCELLATION 4 AUTO CALL BACK (ACB) 94 AUTO CALL BACK CANCELLATION 97 CALL FORWARD ( Not activated ) 98 CALL FORWARD CANCELLATION CALL CONSULTATION – On(IC or OG) call ,FLASH followed by

telephone number CALL TRANSFER : On (IC or OG) call , FLASH followed by

telephone number then ‘ON – HOOK’ the telephone THREE PARTY CONFERENCE : First step: On incoming call, flash followed by 2nd party telephone number

Second step: flash + ‘*’3

TIME ANNOUNCEMENT : DIAL – 174 AUTOMATIC COMPLAINT LOGON : DIAL – 198

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Parallel telephone ringing : On IC call FLASH and ‘ON-HOOK’ the telephone – you will get ring again

FLASH is provided in all the new PB instruments or it can be done by just tapping of ‘Cradle Switch’ of any telephone instrument

ADVANTAGES WITH THE MODERN ELECTRONIC

EXCHANGE:

Central exchange built in compact, space, saving

construction practice.

Absolute operational reliability even in dusty of corrosive

environment

No routine maintenance

Simple but comprehensive check of the entire system,

from the central exchange

Removal of faults by exchange plugs-in-cards

Simplex expansion of a central exchange due to its pre-

wiring for acceptance of additional plug in cards at a later

stage

No skilled personnel required for trouble shooting, unless

for troubles are severe

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A high grade electronic design and rugged mechanical

construction ensure reliable operation of a system, Inter

stations can be expanded on a building block basis, while

central exchange can be put together individually

This exchange

CONCLUSION

In this modern age industrialization and automation,

telecommunication plays a vital role in coordinating the activities in

achieving the assigned targets and accomplishing the desired

performance in any organization. However, miniaturization and

faster accessing modes developed using the latest technologies may

further bring various technological departments in the field of

communications. With the advancements in electronics more

sophisticated exchanges with more number of applications may be

available to the human world thus, making the communication

easier.

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BIBLIOGRAPHY

1. Alcatel Lucent OXE cabinet Manual

2. Communication Systems

- George Kennedy

3. Telecommunication Switching Systems And Networks

- Thiagarajan Viswanathan

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