MTNL

Mahanagar (Big city) Telephone Nigam(Enterprise) Ltd.

Mtnl was established in 1986 and is a joint venture with more than 50% share being owned by the govt of India.

Mtnl provides various services in telecommunication sector such as providing landline, wireless communication etc and is the first company to launch the 3G services is India.

Mtnl has also widen its range outside India by establishing itself in countries like Mauritius & Sri lanka and has recently entered American market.

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OBJECTIVES

To study different types of telephone

switches used in the field of telecommunications such as alcatel ocb, siemens ewsd etc. during six

weeks of industrial training from (31st may to 9th july 2010).

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TELEPHONE SWITCHES

In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls. A central office is the physical building used to house inside plant equipment including telephone switches, which make telephone calls "work" in the sense of making connections and relaying the speech information. Some commonly used switches are:

OCB- 283 5ESS EWSD

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CONTENTSIntroductionSalient featuresGeneral Architecture of OCB-283Subscriber access unitTrunk & Junction connection unitControl unitsTime base generatorOperation & Maintenance unitBattery Specifications

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INTRODUCTION

OCB 283: Organ control board 2nd gen microprocessor version 83.

OCB-283 is digital switching system which supports a variety of comm. Like basic telephony, ISDN, interface to mobile comm., data comm. Etc.

The first OCB-283 exchange of R-11 version was commissioned in FRANCE & Beijing, CHINA.

The first OCB-283 exchange came to INDIA in 1993,subsequently the system has been upgraded, R-20 was fully validated in January 1994.

There after time to time up gradation to this OCB-283 SYSTEM was upgraded to R-25.

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Salient features of OCB-283 It is digital switching system with an angle “T” shape switch.

A maximum of 2048 PCM can be conducted. Its supports both ANALOG and DIGITAL subscribers. OCB-283 has a double recovery feature. Various units of 0CB-283 system are connected over token

ring. This enables fast exchange of information & avoid complicated links.

The charge account of subscriber are automatically saved in a disk once in a day , this avoid lose of revenue in case of total power supply failure.

All the control units are implemented on same type of hardware. This is called a station.

The ocb-283 systems are made up of 35 types of cards. The system has modular structure . The expansion can be

very easily carried out by adding necessary hardware & software.

The Environment requirement of the system is very flexible. The system can work at temp. 5-45°C ; though optimum temp. is 22°C.

OCB-283 ARCHITECTUREOCB-283 COMPRISES OF FOLLOWING 3

SUBSYSTEMS

SUBSCRIBER ACCESSSYSTEM

CONNECTIONAND

CONTROL

OPERATIONAND

MAINTENANCE

CCITT #7SIGNALLING NETWORK

TELEPHONE NETWORK

DATANETWORK

VALUEADDED NETWORK

O&MNETWORK

DISK

MAGTAPEPABX

SUBSCRIBER ACCESS SUBSYSTEM

CONTROL & CONNECTION SUBSYTEM

OPERATION & MAINTENANCE SUBSYTEM

OCB-283

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OM TX TR MR MQ GX PC

COMETA

PUPE

SMT

CSNL

CKTS

LR (4MB / S)

LR

LR

COMMUNICATION MULTIPLEXTMN

2 MB/SPCM

CSND

SMA

SMX

SUBSCRIBER ACCESS SUBSYSTEM

CONNECTIONSUBSYSTEM

CONTROLSUBSYSTEM

O & M SUBSYSTEM

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Subscriber Access UnitSubscriber access unit (CSN) is so designed that they can be

equipped with analog or digital subscriber or both. The cards for both are different but they can be equipped in any slot of the shelf.

CSN can be placed either in EXCHNAGE switch room or at a remote location. CSN is known as CSNL or CSND.

Connection & Control Units:

Multi register (MR):- Call handler setup and release of call. Translator (TR):- Translation of digits, databanks of subscriber & circuits in

files. Marker (MQ):- Message distribution between common control & connection

units. Charger (TX):- Computing the charges of a call, keeping meter. Matrix System Handler (GX):- Process & make connection in switching

matrix on the order from MR or MQ. Common Channel signaling Network Controller(PC):- Manage the CCS#7

network for signaling.

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Operation & Maintenance Unit (SMM)

SMM station in ocb-283 performs the O & M functions. The SMM station has full duplicate hardware SMM A & SMM

B. For both SMM there are two mirror image hard disks of 1200

MB capacity. SMM dialogue with all SMCs over MIS token ring.

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TRUNK & JUCTION CONNECTION UNIT(SMT)

This is also known as PCM trunk control station. This unit is an interface between PCM junction coming from other exchange & switch. The current version of SMT in India is SMT 2G.

In each SMT 2G , there are 8 modules & in each module there are 16 PCMs. Thus there are 128 PCMs, in single SMT 2G. SMT 2G is built around microprocessor 68030.

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Time Base Generator (STS)

Time base generator is required to synchronize PCM links connection units like CSNL,SMT & SMA etc. The time base is generated by synchronization and time base station (STS) & distributed to the branches of the switching network.

These branches then redistribute the time base to connection units along with LRs.

EXCHANGEA

EXCHANGEC

EXCHANGEB

COMMON SIGNALLING CHANNEL

VOICE CHANNELS

OCB-283 FOLLOWS CCITT-NO 7 SIG.PROTOCOL FOR

COMMON CHANNEL SIGNALLING

SIGNALLING TIME SLOT LINK CARRIES ALL THE SIGNALLING FOR ALL THE VOICE CHANNELS BETWEEN

TWO EXCHANGES

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CALL PROCESSING

CKTS

OM

TR MR MQ GX PC

ETA

TX

MAS

MIS

SC SC

SC

SMX

COM

CSNL

CSND

CSNL

VC VC

SC

SMT

PU/PE

SC: Signaling channelVC: Voice channel

NEW CALL MESSAGE COMES ON SIG.CHANNEL SC TO PU/PE WHICH DETECTS ERRORS

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CKTS

OM

TR MR MQ GX PCTX

MAS

MIS

SC SC

SC

SMX

COM

CSNL

CSND

CSNL

VC VC

SC

SMT

ETA

SC: Signaling channelVC: Voice channel

‘A’ ‘B’

PU/PE

NEW CALL MESSAGE IS SENT TO MR BY PU/PE. tr provides subs data to mr.

mq provides address of vc on smx to mr.

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CKTS

OM

TR MR MQ GX PCTX

MAS

MIS

SC SC

SC

SMX

COM

CSNL

CSND

CSNL

VC VC

SC

SMT

ETA

SC: Signaling channelVC: Voice channel

‘A’ ‘B’

PU/PE

MR ORDERS SMX FOR CONNECTING DIAL TONE TO CALLING SUBS

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CKTS

OM

TR MR MQ GX PCTX

MAS

MIS

SC SC

SC

SMX

COM

CSNL

CSND

CSNL

VC VC

SC

SMT

ETA

SC: Signaling channelVC: Voice channel

‘A’ ‘B’

PU/PE

FIRST DIGIT IS RECEIVED VIA VOICE CHANNEL VC IN ETA ETA SENDS IT TO MR ON MASDIAL TONE IS CUT OFF ON ORDERS OF MR

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CKTS

OM

TR MR MQ GX PCTX

MAS

MIS

SC SC

SC

SMX

COM

CSNL

CSND

CSNL

VC VC

SC

SMT

ETA

SC: Signaling channelVC: Voice channel

‘A’ ‘B’

PU/PE

ROUTING OF CALL -MR ORDERS CSN-B TO TEST ‘B’ & GIVE VC FOR ‘B’CSN-B TESTS ‘B’ AND GIVES RINGING TO ‘B’ SMX GIVES RBT TO ‘A’

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SC: Signaling channelVC: Voice channel

‘A’ ‘B’

CKTS

OM

TR MR MQ GX PC

A B

TX

MAS

MIS

SC SC

SC

SMX

COM

CSNL

CSND

CSNL

VC

SC

SMT

PU/PE

CALLED PARTY B GOES OFF HOOKCALLED PARTY’S CSN SENDS LOOP CONDITION & VC-B GIVES INFORMATION TO MR OVER SC VIA PU/PERINGING CURRENT & RBT ARE STOPPED

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‘A’ ‘B’

CKTS

OM

TR MR MQ GX PCTX

MAS

MIS

SC SC

SC

SMX

COM

CSNL

CSND

CSNL

VC-A

SC

SMT

SC: Signaling channelVC: Voice channel

PU/PE

VC-B

‘A’ ‘B

CKTS

OM

TR MR MQ GX PCTX

MAS

MIS

SC SC

SC

SMX

COM

CSNL

CSND

CSNL

VC-A

RGF

SC

STM

SC: Signaling channelVC: Voice channel

PU/PE

VC-B

TWO UNIDIRECTIONAL CONNECTIONS ARE ESTABLISHED IN SMX ON ORDER OF MR VIA GX‘A’ & ‘ B ‘ CAN NOW CONVERSECHARGING IS STARTED BY TX - MR RELEASED

Happy talking!!

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OCB-283EXCH

AND YOUR METER

IS RUNNINGHERE!!!

Battery Specifications

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Switch Type

Battery Capacity

Manufacturer

Status

Life Operating vol.

Ocb-283

4000Ah

Maharaja

Maintenance free

7 years Approx.

-48

REFERENCES

www.wikipedia.org www.mtnldelhi.in www.bsnl.com www.alcatel.com Device manual

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