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CHAPTER 1

INTRODUCTION TO

TELECOMMUNICATION

Telecommunication is the process of providing long

distance telephonic or telegraphic information was also a

myth about 106 years before. Hearing voices when there

was no one around was looked upon as a manifestation of

either mystical communication or insanity. But undaunted

by the rebuffs of the people, the great scientists like graham

bell and Morse sowed the seeds so deep that we have now a

beautiful blossoming and ever increasing tree of

telecommunication.

Though the scientific discoveries of electricity and

magnetism, which resulted in the development of telegraph

system, were equally valid for telephone, the first practical

development (foe speaking) system was invented by

ALEXANDER GRAHAM BELL in 1876, about 40 years

after the invention of telegraph system.


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In 1928, there was invention of combined hand micro

telephone properly known as FRENCH

TELEPHONE . The ringing bell and other componentsgot placed inside the instrument itself in 1923.

This lead to the idea of telephone exchange, a centralized

place with some equipment to make it possible for

interconnection of telephone users. The first to come was

MAGNETO SYSTEM. This used a local battery and the

hand generator to call the exchange. The operator in the

exchange then connects the calling subscriber to the called

subscriber by sending a ringing current on the called

subscribers line. This manual telephone exchange suffered

from many disadvantages. To overcome these, an

automatic telephone system was developed. This

eliminated the use of operator at the exchange. The

telephone instrument at the subscriber premises was

provided with a number and the exchange equipment was

so designed that it responded to the dialed number and

could connect the calling subscriber to the called

subscriber. The first automatic dial telephone system

patented in 1891 by ALMON.B.STROWGER, used


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selector principle for the exchange equipment. The manual

and automatic changes were also used to cater for trunk

traffic i.e. to make two persons located in two differentplaces to speak to each other. The first trunk telephone

service that came into use was as early as 1891 between

London and Paris. This used a heavy copper conductor pair

of wires between two stations.

To provide both telephone and telegraph circuits between

two stations, coaxial and microwave systems were evolved.

We have now as many as 2700 speech circuits between two

stations. These systems can also transmit television signals

and provide 1200 speech and one T.V. channel between

two stations.

1957 saw the dawn of man-made satellite. The U.S.S.R in

October 1957 placed in orbit SPUTNIK 1, that was

followed by EXPLORER 1 by U.S.A three months later.

This inspired the telecom engineers to evolve

communication satellites. In 1962, Telestar relayed the live

T.V. across the Atlantic for the first time.


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In India, domestic satellite system became operational in

June 1981 and made fast and high quality communication

possible in far areas like Leh, Mizoram, Port Blair.

Telecommunication engineers are trying to realize the

dreams not only to hear the sweet voice of their beloved

ones but also enjoy their visual gestures. Picture telephony

is already operational in U.S.A.

Yet another development in the field of telecommunication

is mobile communication. In U.S.A, one can dial the

wanted number within 50 kms while driving a car.

To conclude we can say that the history of

telecommunication is no less interesting than the history of

man. From its primitive stage it has become one of the most

sophisticated branch of engineering. There seems to be no

end on this field.


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CHAPTER 2

INTRODUCTION TO OCB-283

The ALCATEL 1000 E10(ocb-283) exchange is also

known by its short name as the E10 (OCB-283). CIT

ALCATEL OF FRANCE has developed this system. It

stands for Organ Controlled Version B (using second

generation of 83 series of microprocessor). It is the digital

switching system, which supports a variety of

communication, needs like basic telephony, ISDN,

interface to mobile communication etc.

The first OCB exchanges of R 11 version were

commissioned in Brest( France) and Beijing (China) in

1981. The first OCB-283 exchange came in India in 1993.

Subsequently the system has been upgraded and current

versions R-21, R-22 are being supplied. The basic

architecture remaining same, more facilities both to


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subscribers and administration are supposed by later

versions.

It has modular architecture, which means that new services

can be added and processing capacity can be increased

without interrupting operation of the exchange. The E10

(OCB-283) exchange is multipurpose exchange.

Subscribers connected in OCB-283 exchange on digital

subscriber center CSN equipments. The CSN equipment is

especially developed to make the subscriber access system

quite independent of the exchanges common equipments.

OCB-283 switching system is capable to connect both

analog and digital subscribers. Digital subscriber center

(CSN) is therefore designed to serve both analog and

digital subscribers.


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2.1 SALIENT FEATURES OF OCB-283

It is digital switching system with single T stageswitch. A maximum of 2048 PCMs can be connected.

It supports both analog and digital subscribers. The system supports all the existing signaling systems

like decades, MF, CAS and CCS#7 system.

It provides telephony, ISDN, data communication,cellular radio and other value added services.

The system has automatic recovery feature. It has a double remoting facility. Subscribers access

unit CSDN can be placed at the remote place and

connected to the main exchange through PCM links.

The charge account of subscribers are automaticallysaved in the disc once in a day avoiding loss of

revenue in case of power failure.

The traffic handling capacity of the system is huge. Itcan handle 800000 BHCA and 25000 Erlangs of

traffic.


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All the control units are implemented on the same typeof hardware. This is called station. For all these

control units, only one backup station is provided,enabling automatic recovery in case of fault.

The OCB-283 is made of only 35 types of cards. Thisexcludes the cards required for CSN.

The system has modular structure. The expansion canbe very easily carried out by adding necessary

hardware and software.

The SMMs are duplicated, with one active and otherin standby. In case of faults, switch over takes place

automatically.

The space requirement is very small. No separateroom is required for OMC. There is no fixed and rigid

rack and suite configuration in the system. It provides

great flexibility and adjustment in the available space.

The environment requirement of the system are veryflexible. The system can work at temperature 5 to 45


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degree Celsius though the optimum temperature is 22

degree Celsius.


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CHAPTER 3

ARCHITECTURE OF THE ALCATEL

1000 E10 (OCB-283)

The E10(OCB-283) is constructed according to thefollowing principles:

It has modular architecture. System functions are distributed over its components

modules. The principle of modularity is applied to

both hardware and exchange software.

3.1 THE SYSTEMS MODULAR

ARCHITECTURE MEANS:

EASE OF MODULATION: The number ofdifferent modules can be tailored to the function of

exchange performs as well as the volume and

characteristic of the traffic handled.


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RELIABILITY: Newly developed modules are testedindependently.

DEPANDABILITY: The principle of redundancy isapplied to each types of system components.

Redundancy ensures continuity of service if a unit

fails.

EASY UPGRADE: It is easy to add new modules toaccommodate for technological changes.


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Fig 3.1 :- General Architecture of OCB- 283

3.2 THE E 10 (OCB 283) CONSISTS MAINLY

OF:

Control Stations Software Machines A communication local area network

3.2.1 Control Stations:

The SMs (control station) are the hardware modules of the

E10 OCB-283. An SM is a set of boards in a sub rack. The

boards supporting the processors and the memories are

linked together via a bus. Each SM is connected to the

communication local area network.

FIVE TYPES OF SM :

SMCs (main control station) supporting the switchingfunctions (charging, translation etc.)

SMTs (trunk control stations) supporting the auxiliaryfunctions.


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SMXs (matrix control stations) which comprises theswitching matrix.

SMM (maintenance station) for operating andmaintaining the system.

3.2.2 Software Machines:

The MLs (software machines) are the software modules of

the E 10 OCB-283. An ML is supported by a control

station. Several MLs can coexist on the same SM.

The ML SM (control station software machine) is present

in every SM. It operates the station. The other MLs called

functional MLs are for the exchanges main function (call

handling, connection management etc.)

3.2.3 Local Area Network :

The local area network links the SMs together. It supports

communication between the software machines supported

by the SMs. One ML can communicate with another

needing to know where it is in the network. The local area

network consists of upto five multiplexes.

MAIN CONTROL STATIONS(SMC) :


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The SMCs handle the following control functions:

Call handling (setting up disconnecting call). Translation (managing routings and charging modes

based on data bases).

Charging. Circuit Observation. Connection Management. Signaling network management. Server Management

The SMCs also have a particular role in the communication

local area network. The SMCs are connected to theMIS(intra station multiplex) and to the MAS (main control

station access multiplex). They can communicate with all

the stations on the local area network and convey messages

between SMs connected to different multiplexes.

TRUNK CONTROL STATION (SMT):

The SMT (trunk control station) are for connecting the

PCM links and processing the channel associated signaling.


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The SMTs are the interfaces between the E 10 OCB-283

and the remote network elements (exchanges, subscriber

connection units etc.)

There are two SMT versions:

The SMT1G capable of connecting 32 PCM links.

The SMT2G capable of connecting 128 PCM links.

SMT1G:

An SMT1G comprises:

A duplicated control logic that operates in workerstandby mode.

Interfaces with the PCM links. Interfaces for connetion to the two branches of the

switching matrix system.

SMT2G:

An SMT2G comprises:

Two individual stations, SMTA and SMTB, whichcontrol the SMT and operate in worker-standby mode.

Each individual station has the basic control station


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equipment (CMP, PUP, common memory) and

adapters linking with the ETs (exchange terminations).

AUXILIARY EQUIPMENT CONTROL STATIONS

(SMA):

The SMAs (auxiliary equipment control stations) house the

systems auxiliary(service circuit) equipments.

The SMAs functions are:

1.Management of voice frequency signals: Receipt and generation of frequencies for

setting up.

Calls. Management of conference circuits. Tone Generation.

2.Time management.3.Processing of No.7 common channel signaling.

An SMA contains the basic SM equipment plus,

depending on requirements, adapters dedicated to the

functions listed above.


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SWITCHING MATRIX SYSTEM (SMX):

The SMX (switching matrix system) sets up the

connections between the different slots that come from the

connection units (local SMT, SMA and CSN). It comprises

of two identical branches each with a switching matrix. For

each call, the connections are set up simultaneously in both

branches. A control unit selects the branch that is active for

that call. The SMXs two-branch structure provides

connetions defence capability.

SWITCHING MATRICES:

The matrix of the SMX are square matrices(the same

number of outgoing links and incoming links). They consist


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of basic elements called time switches, they can switch

time slots from 64 LRS.

The juxtaposition of the time switches increases the

capacity of a switching matrix to 2048 LRE by 2048 LRS.

To increase the capacity of the switching matrices, all that

is required is to add the equipment that supports new time

switches. So switching capacity can be increased

progressively as required with lack of continuity. Each

connection uses a single switch. The SMX therefore has

only time stage T.

This feature ensures that:

There is no blocking. Call setup time are short. Cross-office time is the same for all connection.

SYNCHRONISATION AND TIME BASE STATION

(STS):

The STS(synchronization and time base station) generates

the timing signals needed to process digital data.


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The three oscillators used to generate the timing signals

from the BT(time base).

All these are powered independently.

The timing signals delivered by the STS are transmitted to

both branches of the SMX. In each branch, a majority logic

selection mechanism chooses the timing signal which is

distributed in the matrix and then to the SMAs, SMTs and

CSNLs.

The STS can operate in different modes:

SYNCHRONISED:

An external synchronization is used.

STANDALONE:

There is no external synchronization link. The

synchronization interface provides the BT with a reference

frequency.

FREE RUNNING OSCILLATOR:

There is no synchronization interface.

CONTROL UNITS:


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These units provide control of calls on the basis of stored

programs. They process the calls on reception of dialed

digits from calling subscribers and take part in handling ofcall setup and release by processing, monitoring,

measuring, charging of calls and all the common control

functions needed for the working of an automatic common

control exchange. These control units can comprise of

following functions.

MULTI REGISTER (MR):

The MR establishes and releases the calls. It takes real time

decisions for processing of a call. MR consults TR to find

out subscribers entitlement and stores digits dialed by the

subscriber.

It also orders for connections and disconnection of various

tones and subscribers.

In addition of call processing functions MR also carries out

testing of circuits and observational functions.

TRANSLATOR(TR):

The TR stores the exchange database in its memory. On

request, it will tell MR the characteristics and entitlements


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of subscriber and circuits. The TR also stores routing and

analyzing data. It converts the received digits into

equipment no. of the called subscriber.

MARKER(MQ):

The market carries out connections and disconnections

between subscribers or circuits. It also acts as gate for

messages, which pass from one communication domain to

another. The MQ also supervises semi permanent

connections in the network.

CHARGING UNIT (TX):

As the name suggests, the TX carries out charging of each

communication setup. It also keeps charge amount of all

subscribers. The TX also prepares and sends detailed

billing messages to SMM. In addition, it also carries out

subscribers and circuit observation functions.

MATRIX SYSTEM HANDLER (GX):


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The GX monitors the connections in the switching network

and in case of fault, carries out appropriate defense

function.

COMMUNICATION LOCAL AREA NETWORK :

The local area network supports communication between

the SMs (control stations) of the E-10 OCB-283.

The local area network comprises of up to five

communication multiplexes:

The MIS( intra station multiplex) supports the transferof messages between the different SMCs and SMMs.

The MAS(main control station access multiplex)support the transfer of messages between the SMCs

and the SMAs, SMTs and SMXs. Depending upon the

configuration upto four MASs are on the network.

In a compact configuration, the local area network has only

one communication multiplex(than MIS) to which all the

SMs are connected.

All the communication multiplex, MIS and MAS have the

same characteristics. A multiplex consists of two


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transmission media in a ring and transfers using the token

ring protocol. Both the multiplex rings operate in load

sharing mode. However, each ring is capable of handlingall the traffic on the multiplex. So duplication of ring

safeguards the transfer of all the messages.

MAINTENANCE STATION (SMM):

Role of the maintenance station:

The SMM (maintenance station) is for:

System management (administration, configuration,initialization)

Operating the exchange. Supervising the system and its environment (defense,

alarms).

Maintaining the equipment (tests,settings). Storing the data.

The control and connection units can operate

independently, but it is the central defense function handled

by the SMM that ensures continuity of service.

BACKUPS:


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THE DISK DRIVES:

Two hard disks are used to store all the systems software

and data. They operate in mirror mode, which means that

data is written in parallel on both disks irrespective of

which subsystem is the worker.

The disks are also used for temporary backup of itemized

billing information.

MAGNETIC TAPE UNIT:

It is possible to copy the information stored on hard disk to

tape, for example, to send the information to a processing

center. The tape drives are fitted with formatting devices.

The tape drives are optional.

STREAMER:

The streamer is used mainly for loading the system at the

outset. It is also used for routine backup operation.


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Table 1 Below shows the number of units used in the

system in a minimum configuration and a maximum

configuration :

EQUIPMEN

T

MINIMUM

CONFIGURATIO

N

MAXIMUM

CONFIGURATIO

N

SMC 2 12

SMA 2 64 including up to :

31 with ML ETA

14+1 with ML

PUPE

16 pairs with ML

AN

SMT2G (With

2 basic

stations per

1 (with 48 PCM

links)

16 (with 128 PCM

links)


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SMT)

SMX (for

each of the 2

branches)

1 (with 80 LR) 8 (with 256 LR)

SMM (with

two

processors

subsystem)

1 1

STS 1 1

Local network

(MIS and

MAS)

1 MIS 1 MIS & MAS

CHAPTER 4

SUBSCRIBER FACILITIES PROVIDED

BY OCB-283


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OCB-283 provided a large number of subscriber facilities.

Some facilities are available only to digital subscribers and

as such they cannot be availed by analogue subscribers. Toavail these facilities numbers are given special categories

by man machine commands.

4.1 FACILITIES TO ANALOGUE

SUBSCRIBERS:

A line can be made outgoing only or incoming only.

Immediate Hot Line Facility: The subscriber isconnected to another predetermined subscriber on

lifting the handset, without dialing any number.

Delayed Hot Line Facility: When subscriber lifts thehandset, the dial tone is provided and subscriber can

dial any number. But if he does not dial any number

within a predetermined time, he is connected to

predetermined number.

Abbreviated Dialing: The subscriber can record ashort code and its corresponding full number in the


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memory. Later to dial this number, he has to dial only

the short code.

Call forwarding: When activated, incoming calls tothe subscriber gets transferred to the number

mentioned by the subscriber while activating the

facility.

Conference between Four Subscribers: Thesubscribers A and B while in conversation can include

two more subscribers by pressing flash button and

dialing their numbers.

Call Waiting Indication: When a subscriber isengaged in conversation and if he gets an incoming

call, an indication is given in the form of tone. Hearing

this subscriber has the option, either to hold the

subscriber in conversation and attend the waiting call

or to disconnect this subscriber and attend to the

waiting call. In the former case, he can revert back to

the earlier subscriber.


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Automatic Call On Busy: If this facility is activatedand if the called subscriber is found busy, the calling

subscriber simply replaces the receiver. The systemkeeps watch on the called subscriber and when it

becomes free, a ring is given to both the subscribers.

On lifting they can talk to each other.

Malicious Call Identification: When this category isgiven to a subscriber, the phone number of calling

subscriber is printed on the called subscribers

telephone terminal.

4.2 FACILITIES TO DIGITAL SUBSCRIBERS

Digital subscribers are provided with all the facilities

available to analogue subscribers. In addition, they are

provided with the following facilities, which are called

ISDN services. An ISDN subscriber can use many

electronic devices on its telephone line and can utilize them

for two or more simultaneous calls of either

VOICE DATA


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VIDEOThe following is the list of some of the services to

the digitals subscribers

A) 64 Kb/s digital connectivity between twosubscribers for data communication.

B)Group 2, 3 or 4 Facsimile ( FAX) services.C)Videotext services.D) Display of calling subscriber number on called

subscribers telephone.

E)Facility for restriction of display of calling subscribernumber on called subscribers terminal.

F)Facility of displaying the connected on the callingsubscribers termainal. This is useful when called

subscriber has activated call transfer facility. The

calling subscriber can choose to speak on forwarded

number or disconnect the call.


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G) Charging Advice: The system is capable ofproviding charging advice either in real time or at the

end of the call.

H) User to User Signaling: The system permitstransfer to mini messages between calling and called

subscribers during call setup and ringing phase.

I)Terminal Portability during the Call: A subscriber canunplug terminal, carry it to some other place or room

and resume the call within 3 minutes.

J)Listening Unanswered Calls: The numbers of callingsubscribers, who call during the absence of the called

subscribers, are recorded in called subscribers

terminal. The called subscriber can then check up

these numbers and call them back, if he wishes so.


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CHAPTER 5

CALL CONNECTION

The interchange of signaling information can be illustrated

with the help of a typical call connection sequence.

A) A request for originating a call is initiated whenthe calling subscriber lifts the handset.

B)The exchange sends dial tone to the calling subscriber

to indicate to him to start dialing.


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C)The called number is transmitted to the exchange,

when the calling subscriber dials the number.

D) If the number is free, the exchange sends ringingcurrent to him.

E)Feed back is provided to the calling subscriber by theexchange by sending:

Ring back tone, if the called subscriber is free. Busy tone, if the called subscriber is busy. Recorded message, if the provision exits for non-

completion of call due to some other constraint.

F)The called subscriber indicates acceptance of theincoming call by lifting the Handset.

G) The exchange recognizing the acceptanceterminates the ringing current and the Ring back tone

and establishes the connections between calling and

called subscriber.

H) The connection is released when either subscriberreplaces the handset. When the called subscriber is in

the different exchange, the following interchange


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CHAPTER 6

TONES AND RECORDED

ANNOUNCEMENTS

A tone is an audible indication comprising a number of

discrete frequencies, but excluding speech. An audible

indication is understood to be a sound composed of

frequencies within the range 300-3400 Hz which is used to


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inform the user about the state of a telephone call or

supplementary service.

Announcement is, on the other hand, a recorded speech

sample and is switched to the time slots destined to the user

to whom the announcement is to be fed. The use of

announcement is made in such circumstances, which

necessitate communication of special information to the

user in order to prevent repeated and anfractuous call

attempts.

6.1 ADVANTAGES OF RECORDED

ANNOUNCEMENTS:

Some factors make recorded announcements attractive.

They can reduce the level of call to operators, thussaving considerable expanse.

From human factors point of view, the use of anexcessive number of different tones can be confusing

to the user. Recorded announcements give an

opportunity to present a far greater spectrum of

information and are also more human.


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Recorded announcements can impart more detailedand specific information than tones.

Recorded announcements may have less chance ofbeing misunderstood than tones in situations

encountered frequently.

6.2 CLASSIFICATION OF TONES:

Basic Tones: These are tones related to the basicservices and features.

Service Tones: These are the tones relating ti theusage of supplementary, non-supplementary and other

services.

Test Tones: These are the tones used by theadministration for maintenance and diagnostic

services.

6.3 CLASSIFICATION OF RECORDEDANNOUNCEMENTS:


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Called subscriber related: These recordedannouncements are fed to the calling subscriber and

pertain to the called subscriber number an his line.

Calling subscriber related: These recordedannouncements are also fed to the calling subscriber

and related to his own number.

Route Related : These recorded announcements arefed to the calling subscriber to provide information on

the route (i.e. the first few digits) dialed.

Exchange related: These recorded announcements arefed to the calling subscriber and pertain to his local

exchange (i.e. status of the exchange).


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CONCLUSION

The OCB system is inherently provided with flexibility to

meet the future telecommunication needs and challenges. Itis hoped that its introduction will pave the world for the

rapid digitalization if our network.

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