Post on 03-Apr-2018
transcript
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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.