Industrial Training Record BSNL Kodad

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Anurag College of Engineering, KODAD Bharat Sanchar Nigam Limited, KODAD
INDUSTRIAL TRAINING RECORD
FOR 6 MONTHS INDUSTRIALTRAINING
TELEPHONE EXCHANGE KODAD
at
KODAD SUB DIVISION - NALGONDA SSA AP CIRCLE
**************************************************************
A training report
Submitted by
K GOPI KRISHNA (DEEE)
In fulfilment of completion of 5th
semester of
Diploma in Electronics and Communication Engineering
for 2012-15 batch from
Anurag Engineering College KODAD.

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ACKNOWLEDGEMENT
It is with profound gratitude that we express our deep indebtedness to
all the employees of B.S.N.L. without whose support and guidance it would not
have been possible for this training to have materialized and taken a concrete
shape. We owe my personal thanks to my trainers in charge –Sri. V Srinivasa
Rao SDE, Sri D Upender Reddy JTO and Sri K Gopi Krishna TTA who extended full
support and co-operation at every stage of our training period. We would also
like to take this opportunity to acknowledge the guidance from Mr. N Ravi
Kumar (HOD of electronics and communication) and Ms. G Shobha and Ms. V
Swapna (Seminar Co-ordinators of electronics and communication) for
undergoing training at a reputed company like B.S.N.L.
We are also indebted to our parents, our batch members and friends for
their constant encouragement and helping us in my endeavour. Last, but not the
least, we would like to thank everyone who has contributed for the successful
completion of our training.
Our training batch members from DECE branch, Anurag Engineering College
Kodad
1) B Triveni 12274-EC-252
2) D Gayathri 12274-EC-211
3) D Triveni 12274-EC-253
4) G Akhila 12274-EC-201
5) G Anusha 12274-EC-202
6) L Shireesha 12274-EC-241
7) R Sirisha 12274-EC-242
8) T Madhuri 12274-EC-219
9) T Navya 12274-EC-227
10) T Swathi 12274-EC-251
11) V Divya 12274-EC-209

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PREFACE
Organizations are made up of people and function through people.
Without people, organizations cannot exist. The resources of men, money,
material, machinery, and mechanism are connected, coordinated and utilized
through people. Engineers need to concentrate more on mechanism and the
way in which things have been made. The need of training arises for doing
things yourself, understanding its way.
Practical exposure for doing things makes a person conversant to the
technicalities involved in any job. In view of such benefits, imparting of
vocational training has been made an integral part of any academic structure.
In B.S.N.L., training is given to Engineering Aspirants to secure future in the
dynamic world of telecommunications. Today telecommunication industry is
one of the very fastest growing industries in the world.
It is very important to know the applications of different technologies
before knowing the fundamentals of their theory. We have seen practically so
many communication equipments and their working and also known some of
their maintenance procedures. We clearly understand that imagination of our
theoretical studies is now easier than before this practical training.
In this order we have taken 6 months BSNL training. In our report, we try to
follow the stated objectives in curriculum (C-09) of our academic 5th
semester.
BSNL staff also provided that facility to follow those objectives stated below as
per our curriculum.
1) Organizational setup
2) Raw materials
3) Various stages of processing and arrangement of equipments
4) Quality control
5) Trouble shooting
6) Safety precautions
7) Various pollutants
We also try to introduce all the equipments installations for providing
various services by BSNL like Landline, Broadband ADSL, Leased line concepts,
MLLN, GSM, WIMAX, Wi-Fi, OFC Systems like STM, Overview of Intranet and
Electrical Power Supply systems like batteries and power plant.

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Table of content
Sl.No. Description
Page
No.
1 1. 0 Introduction to BSNL 6
1.1
Various Dept and
sections 9
2 2. 0 Raw materials and store
3 3. 0 Various stages involve in processing of Different equipments
and technologies, their sequential arrangement and their
trouble shooting and preventive measures.
.
3.1 Landline 11
External Plant, Land line 13
MDF 19
Telephone Exchange 19
Signalling 21
CDOT DSS MAX switch 24
CDOT ANRAX 33
RSU 37
TAX 38
3.2 ISDN 38
3.3 Broadband 39
ADSL 41
ADSL Modem 42
DSLAM 46
BBRAS 48
3.4 Wi-Fi 49
3.5 Leased lines 50
PMUX 53
Leased Line Modems 54
3.6 MLLN 55
3.7 GSM 56
2G BTS 60
3G 63
Introduction to 4G 64
3.8 CDMA WLL 65

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3.9 OFC systems 66
OF Cables 66
FDF 71
DDF 72
CPEs 72
STM-4 74
STM-16 74
3.10 Digital Microwave 74
3. 11 Wimax 76
Wimax Modems 77
3.11 FTTH 78
3.12 BSNL Intranet 79
3.13
Electrical Systems in BSNL
Exchange 81
Sub-Station 83
Engine-Alternators 86
Capacitor bank 86
Bus bar control panels 89
AVR 90
Power Plant 90
VRLA Batteries 92
AC Plant 97
3.14 Why --48V DC 97
4 4. 0 Quality Control in BSNL 99
5 5. 0 Trouble shooting was already coved in the item no 3.0
6 6. 0 Safety 99
Fire safety 99
Earthing 100
Electrical Safety 101
Lightning Protection 101
Cell Radiation safety 101
7 7. 0 Pollutants from BSNL 102
Cell Radiation 102
E-waste 102
Conclusion 103

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Bharat Sanchar Nigam Limited
(abbreviated BSNL) is an Indian state
owned telecommunications compan
y headquartered in New Delhi, India.
It was incorporated on 15 September
2000. BSNL is India's oldest and
largest communication service
provider (CSP). It had a customer
base of 117 million as of Jan 2014.
BSNL has installed Quality Telecom Network in the country & now focusing on improving it,
expanding the network, introducing new telecom services with ICT applications in villages &
winning customer's confidence. Today, it has about
43.74 million..............line basic telephone capacity,
8.83 million................WLL capacity,
72.60 million............ GSM capacity,
37,885...................... fixed exchanges,
68,162...................... GSM BTSs,
12,071...................... CDMA Towers,
197............................ Satellite Stations,
6, 86,644 RKm........... OFC,
50,430 RKm.............. microwave network connecting
623............................ districts,
7330 ...........................cities/towns &
5.8 lakhs ....................villages.
Services offered by BSNL
BSNL provides almost every telecom service in India. Following are the main telecom
services provided by BSNL:
 Optical Infrastructure and DWDM (Dense Wavelength Division Multiplexing) : BSNL
owns the biggest OFC network in India. Also the DWDM network is one of the biggest in
the world.
 Managed Network Services: BSNL is providing complete Telecom Services Solution to
the Enterprise Customers i.e. MPLS Connectivity, Point to Point Leased
Lines and Internet Leased Lines.
 Universal Telecom Services: Fixed wire line services and landline in local loop (WLL)
using CDMA Technology called bfone and Tarang respectively. BSNL had 75% market
share of fixed lines.
 Cellular Mobile Telephone Services: BSNL is major provider of Cellular Mobile
Telephone services using GSM platform under the brand name Cellone & Excel (BSNL
Bharat Sanchar Nigam Limited

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Mobile). As of 30 June 2010 BSNL has 13.50% share of mobile telephony in the
country. It has 95.54million customers using BSNL mobile.
 WLL-CDMA Telephone Services: BSNL's WLL (Wireless in Local Loop)service is a service
giving both fixed line telephony & Mobile telephony.
 Internet: BSNL provides Internet access services through dial-up connection and ADSL
broadband as BSNL Broadband BSNL held 55.76% of the market share.
 Intelligent Network (IN): BSNL offers value-added services, such as Free Phone Service
(FPH), India Telephone Card (Prepaid card), Account Card Calling (ACC), Virtual Private
Network (VPN), Tele-voting, Premium Rae Service (PRM), Universal Access Number
(UAN).
 3G:BSNL offers the '3G' or the'3rd Generation' services which includes facilities like
video calling, mobile broadband, live TV, 3G Video portal, streaming services like online
full length movies and video on demand etc.
 IPTV: BSNL also offers the 'Internet Protocol Television' facility which enables customers
to watch television through internet.
 FTTH: Fibre To The Home facility that offers a higher bandwidth for data transfer.
 Helpdesk: BSNL's Helpdesk provide help desk support to their customers for their
services.
 VVoIP: BSNL, along with Sai Infosystem - an Information and Communication
Technologies (ICTs) provider - has launched Voice and Video over Internet Protocol
(VVoIP). This will allow making audio as well as video calls to any landline, mobile, or IP
phone anywhere in the world, provided that the requisite video phone equipment is
available at both ends.
Vision, Mission and Objectives of BSNL
VISSION:
 Be the leading telecom service provider in India with global presence.
 Create a customer focused organization with excellence in customer care, sales and
marketing.
 Leverage technology to provide affordable and innovative telecom. Services/products
across customer segments.
MISSION:
Be the leading telecom service provider in India with global presence.
 Generating value for all stakeholders - employees, shareholders, vendors & business
associates
 Maximizing return on existing assets with sustained focus on profitability
 Becoming the most trusted, preferred and admired telecom brand
 To explore International markets for Global presence

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Creating a customer focused organization with excellence in customer care, sales&
marketing.
 Developing a marketing and sales culture that is responsive to customer needs mer care,
sales& marketing
 Excellence in customer service-”friendly, reliable, time bound, convenient and courteous
service”
Leveraging technology to provide affordable and innovative products/ services across
customer segments
 Offering differentiated products/services tailored to different service segments
 Providing reliable telecom services that are value for money
Providing a conducive work environment with strong focus on performance
 Attracting talent and keeping them motivated
 Enhancing employees skills and utilizing them effectively
 Encouraging and rewarding individual and team/group performance
Establishing efficient business processes enabled by IT
 Changing policies and processes to enable transparent, quick and efficient decision
making
 Building effective IT systems and tools
OBJECTIVES:
 To be the Leading Telecom Services provider by achieving higher rate of growth so as to
become a profitable enterprise.
 To provide quality and reliable fixed telecom service to our customer and thereby
increase customers confidence.
 To provide customer friendly mobile telephone service of high quality and play a leading
role as GSM operator in its area of operation.
Strategy for:
 Rightsizing the manpower
 Providing greater customer satisfaction
Contribute towards:
 Broadband customers base of 20 Mn in India by the end of 2011-12 as per broadband
policy 2004.
 Providing telephone connections in villages as per Government policy.
To leverage the existing infrastructure of BSNL for facilitating implementation of other
government programmes and initiatives particularly in the rural areas.

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Various Departments and Sections at KODAD Sub-Division
1) Office of The Sub-Divisional Engineer
 SDE is the whole in charge for all the exchanges and cell BTSs working in the area of
KODAD SDCA and for all the staff members.
 The SDE communicates with the superiors and as well as passing orders to the line staff
for execution of various works.
 The SDE monitors, motivates and mobilizes his staff and utilities for better customer
service and for getting better revenue aspects.
2) Commercial Office
 In this mainly dealt with Land line Customer service and revenue like generating orders
for new connection, shifting of telephone, closing of telephone and for providing
additional facilities like ISD and CLIP and Landline customer enquiries and also
maintaining Landline Customer Records.
 Commercial Office uses CRM (Customer Relations Management) software for
generating orders.
3) Customer Service Centre
 In this mainly dealt with the Cell Phone customers service like selling of new sim cards
and their activations, prepaid recharge and top-ups, replacement of lost SIM cards,
selling of prepaid recharge and topup coupons to customers and DSAs (Direct Selling
Agents), RDs (Rural Distributors) of BSNL, and other mobile customer enquiry.
 They use Sancharsoft, CCM (Cellular Customer Manager) and Consumer Mobility
Kenon FX Software for their works.
4) Cash counter
 It receives any type of payments from the customers of BSNL like Landline, post-paid
mobile, WLL phone, Wimax, Leased lines, Landline demand notes and purchase of
materials from BSNL like Broadband Modems in any form like cash, DDs, Checks.
 It uses PMS (Payment Management System) software for receiving payments.
5) JTO Groups office
 JTO Groups is responsible for 10 No.s Rural ANRAX exchanges and their external plants
(UG cable network) and 6 No.s Rural cell BTSs and 1 WLL BTS which are connected to
KODAD MBM and relating line staff.
 They use Clarity software for processing the orders generated in CRM.
6) JTO Phones office
 JTO Phones is responsible for KODAD External Plant(Outdoor), KODAD MBM
exchange(Indoor), 5 No.s cell BTS sites, 1 WLL BTS site and relating staff.
 They use Clarity software for processing the orders generated in CRM.
7) Store
 Store Lineman maintains the store materials like drop wire new telephone
instruments, UG cables, DP and Pillar materials and other exchange materials drawn
from Nalgonda stores in a separate room and maintains material stock register. SLM
works under the control of SDE.

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2.1. VARIOUS RAW MATERIALS (STORE MATERAILS) and Final Products.
Different materials are drawn from Nalgonda Central Stores and kept them at Store
room KODAD and used according to the purpose. One departmental person designated as
SLM (Store Line Man) maintains the store and corresponding material stock register. Various
Materials handled by SLM as follows.
1) LAND LINE:
Phone instruments, Drop wire, LJU boxes, DP boxes, 5 pair cables, Cable
jointing kits, Different underground cables, WILL phones, WLL FCT,FWT, Jumper wires etc..
2) BROAD BAND:
Different modems, ADSL cards for DSLAM etc..
3) MOBILE:
SIM CARDS, Recharge coupons, CTOPUP stock etc..
4) WIMAX (wireless broad band):
WIMAX modems, CAT 5 cable (Ethernet cables) etc..
5) BATTERIES for exchanges and cell BTS sites.
6) DEISEL OIL for Engine Alternator
7) C-DOT CARDS and different electronic equipments for maintenance purpose.
DIFFERENT SCRAPPED MATERIALS:
Used and certified that they cannot usable means not serviceable are scrapped
by the SDE periodically like following materials.
Used and failed batteries
Condemned A/C units
Different failed electronics cards
Final Products
Being BSNL is a commercial organisation final products of it are Different customer Services.
Services Offered at BSNL KODAD
1) Land lines
2) Broad band
3) WIMAX (Closed recently due return of Spectrum by BSNL)
4) CDMA WLL phones
5) Leased lines
6) MLLN
7) GSM 2G&3G Prepaid and Post paid
8) 10 MBPS-NME connections using FTTH
9) Rented buildings and Infrastructure to the Private Operators.

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Arrangement of equipment in schematic manner in less possible area of site.
In BSNL KODAD the equipment like CDOT MBM Switch, Power Plant, Batteries, OFC systems,
Leased line MUX, DDF, MDF and other equipment are arranged systematically for getting
following advantages.
 Less power consumption and less ac requirement
 Less area of occupancy
 Less length of cable connectivity
 Less initial cost
 Easy access for maintenance personnel
Power room should be separated from the electronic equipments SWITCH ROOM, OFC
SYSTEMS, MDF, CELL BTS and other electronic equipments due to power room requires
heavy sized cabling and highly fire prone.
Switch room and MDF are to be arranged very nearly due to all capacity of land line of
switch room should be connected to MDF. And they are also not accessible to the
unauthorised public.
In OFC Room maintenance personnel access should be high. And all the equipment like
rural OFC systems and main OFC systems, DDF, FDF, MUX and VMUX for leased lines,
DSLAM and OCLAN, Cell BTS And WIMAX BTS And other equipment arranged in a systematic
way in order to access for testing and replacement of OFC patch cord 4 wire E1 cables easily.
Various stages involve in processing of Different equipments and technologies, their
sequential arrangement and their trouble shooting and preventive measures.
At KODAD Telephone exchange various equipments and different technologies are using to
provide best customer services. Each service, the corresponding technology and the communication
equipments and their flow charts are listed here and explained in detail. And also mentioned here
some of the maintenance and the trouble shooting procedures of the each equipment.
LANDLINE
Landline: Landline is oldest service provided by BSNL which being extensively in present days also.
Almost 90% of the total Indian villages are already connected by BSNL landline. Actually Landline is a
brand name for the communication service provided by using copper pair from the Exchange to the
Subscriber premises. There are many tariff plans are in use which are changed by area to area. At
Kodad town 99% Landlines are under 110 rupees monthly rent plan with call charges 1.20 rupees for
a call.

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The connectivity diagram of a Landline from the subscriber home to the Nalgonda TAX is shown in
under diagram.

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( External Plant) under Ground cables
BSNL presently uses PIJF UG (Polythene Insulated Jelly Filled Underground) cables for its
underground copper cable network for providing landline telephone services. The construction
features and colour codes are as follows
POLYTHENE INSULATED JELLY FILLED POLYTHENE SHEATHED UNDER GROUND Cables
A) Number of Pairs
The cables shall be in sizes 5, 10, 20, 50, 100, 200, 400, 800, 2000, 2400, 2800, 3200 and 3600 pairs.
In KODAD BSNL we found up to 800 pair cables.
B) Conductors
Each conductor shall be insulated with polyethylene of insulating grade. Different gauges of
conductors 0.32mm, 0.40mm, 0.50mm, 0.63mm, and 0.90 mm are used in the cables. In KODAD we
found that only 0.5mm size conductor cables used.
Each conductor shall consist of a solid wire of annealed high conductivity copper smoothly drawn &
circular in section, uniform in quality, resistance and free from all defects.
The average resistance of all the conductors in the cable shall not exceed the values shown in Table
given below.

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C) Insulation and COLOR Codes
Each conductor shall be insulated with solid medium density polythene of density 0.926 to 0.94 to a
thickness. The insulation should be uniform, smooth and free from all defects. The insulation will
have following color for identifying pairs /conductors under normal lighting conditions.
COLOR CODE FOR WIRE IDENTIFICATION
Primary colors Secondary colors
For 1st
wire in a pair
For 2nd
wire in a pair and binder tape of unit in
50pr/100pr unit
White Blue
Red Orange
Black Green
Yellow Brown
Slate / Gray
A number of twisted pairs laid up to form a group shall constitute the unit. The color scheme of pairs
and wires in a unit shall be read as below.
CODE FOR TAPE OR BINDER FOR UNIT IDENTIFICATION
Unit number 1 2 3 4 5
Color of Binder Blue Orange Green Brown Slate / Gray

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COLOR CODE FOR CONDUCTOR INSULATION
Note:
(a) In 5 pair cable, color code specified for pairs 1 to 5 above is used.
(b) In 10 pair cables and 10 pairs units of 50 pair cables, color code specified for pairs 1 to 10 is
used.
(c) In 20 pair cables and 20 pairs units of 100 pair cables, color code specified for pairs 1 to 20
shall be used.
(d) The number of the pairs with respect to the color scheme is only for the purpose of
identification of pairs, the actual numerical sequence of the pairs varies as the size increase.
The different colors of the binder shall be readily distinguishable under normal lighting conditions.
D) Stranding
A 50 pair cable consists of 5 number of 10 pair units
A 100 pairs cable consists of 10 number of 20 pair units.
These units shall be stranded into a compact and symmetrical cable. the sequence of the units in
the cable shall be same throughout the length of the cable.
An open lapping of 0.02 mm miler tape of any other suitable material of appropriate thickness shall
be applied for each unit.
The tapes shall be so colored and have lay not exceeding 200 mm. This tape is not necessary on the
5 pairs, 10 pairs and 20 pairs cables.
Pair No Color
First Wire Second Wire
1 White Blue
2 White Orange
3 White Green
4 White Brown
5 White Slate / gray
6 Red Blue
7 Red Orange
8 Red Green
9 Red Brown
10 Red Slate / gray
11 Black Blue
12 Black Orange
13 Black Green
14 Black Brown
15 Black Slate / gray
16 Yellow Blue
17 Yellow Orange
18 yellow Green
19 Yellow Brown
20 Yellow Slate / gray
21 Natural Blue
22 Natural Orange
a
b
c

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In case of 5, 10, 20 and 50 pair cables, one spare pair will be stranded as the last pair. The color of
the spare pair shall be in accordance with pair No. 21 of above table.
In the case of 100 pair cable, 2 spare pairs shall be provided. the color of the pair shall be as
specified for pair No. 21 & 22 of above table. The spare pairs in the case of 50 pairs and 100 pairs
cables shall be provided within the cable core, but shall not be within any unit.
The 200pair and 400 pair cables (cables above 100 pr and unto 400 pairs) will be formed by super
units of 50 pairs. and the units stranded in the form of layers
The cable over 400 pairs is formed be the super units of 100 pairs and the units stranded in the form
of layers.
Identification of 50 pair super units in cables of 200 pair and 400 pair & 100 pair super units in
cables of over 400 pairs
Position of the unit in the layer Color binder
First (Marker) Red
Intermediate White
Last (Reference) Black
Note:: The numbering of the units will be clock wise as running end.

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Different configurations of PIJF cables availability is given in table.
Cable size No of Units / Super units
Nominal length in
a drum
In pairs Centre layer Middle Layer Outer Layer 0.50mm 0.40mm
5 1x5 (unit) 1000 -
10 1x10 (unit) 1000 -
20 1x20(unit) 1000 -
50 5x10 (SU) 1000 -
100 5x20(SU) 500 -
200 4x50(SU) 400 -
400 2x50(SU) 6x50(SU) 400 -
800 2x100 (SU) 6x100 (SU) 200 200
1200 3x100(SU) 9x100(SU) 200 200
1600 1x100(SU) 5x100(SU) 10x100(SU) - 200
2000 1x100(SU) 6x100(SU) 13x100(SU) - 200
2400 2x100(SU) 8x100(SU) 14x100(SU) - 200
E) Armouring
When required the cable sheath shall be armoured. For armoured cable a close helical lapping of
waterproof cotton tape shall be applied over the inner-sheath. The cable shall than be armoured
with two applications of galvanized steel tape each applied helically with a gap of 25% + 10% of the
width of the tape, the second tape covering the gap of the first.
F) Overall Polythene Jacket
A tightly fitting jacket of polythene shall be applied on the armoured cable. The minimum thickness
of the jacket shall be 1.2 mm.
USES OF DIFFERENT TYPES OF CABLES
Gauges 0.32 mm and 0.44 mm for primary cable.
Gauges 0.4 mm and 0.5 mm for secondary cable.
Gauge 0.5 mm and 0.63 mm for distribution cable.
Gauges 0.63 mm and 0.9 mm for distribution cable.
Higher gauges of cable for distribution side having longer lengths.
Unarmoured PCUT cable to be laid in duct and to be pressurized.

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Armoured jelly filled cable may be laid direct in the ground and and Unarmoured jelly filled in Ducts
not to be pressurized.
DISADVANTAGES OF PAPER INSULATED CABLES WITH POLYTHENE INSULATED CABLES
 Numbering of pairs is in coded form. Require more skill. Color markings also fade with
due course of time.
 Jointing of cables require skill and perfection is required while plumbing as even a slight
pinhole will cause entry of moisture / water and damage all the pairs.
 Extra care is required for handling like coiling, uncoiling to avoid damage.
 Water / moisture entry will affect the complete cable at once instantaneously.
 Termination in cabinet / pillars / DPs and at MDF is very expensive and time consuming
& increases number of joints.
ADVANTAGES OF POLYTHENE INSULATED JELLY FILLED CABLES.
 Counting of pairs is easy and human mistakes are avoided.
 Jointing is easy and require no chamber or additional place.
 Failure of joints is less.
 Entry of moisture / water is prevented by Jelly in the core.
 Cables can be directly terminated on MDF / Cabinet / Pillar and DPs, thus avoiding
additional joints decreasing the cost and time.
 Handling of cable is easy not delicate like paper insulated cables.
 Life of cable is more.
2) Pillar & DP
The general cable diagram of BSNL network is as follows
Exchange MDF UG cable Pillar DP Subscriber
Pillar
The UG Cable coming from the MDF of Telephone Exchange was directly terminated to the
Pillar. Pillar has a cabinet like structure and number of 100 pair krone modules along with 10 pair
krones is arranged in the pillar to facilitate termination of pairs of primary cable coming from the
MDF and the pairs of secondary cables which are going out to the DPs of that pillar.
Each pillar is numbered for identification. There are 39 pillars are located and covered
several areas of KODAD town. Different Primary cables like 50pr, 100pr, 200pr, 400pr, 800pr are
routed to those pillars. Each Pillar covers a particular area of the subscribers and named with that
area. The capacity of pillars is given by its no. of terminations like 400 pair, 800 pair, 1600 pair etc.

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DP (Distribution Points)
The UG Cables coming from the Pillar are terminated to the different DPs to serve several
customers. DP area is the smallest territory in the cable system. From the DP Subscriber loops are
connected with a over head wire called drop wire. Different size of DPs are 5pair 10pair 20pair. The
size and quantity of krones are depends on secondary cable.
MDF (MAIN DISTRIBUTION FRAME):
M.D.F. is a media between switching network and subscriber’s line. It is a termination point within
the local telephone exchange where exchange equipment and terminations of UG Cable local loops
are connected by twisted pair copper wires called jumper wires.
The MDF is the starting terminating point of all the Primary Underground cables going out from the
Telephone Exchange. There are two sides in MDF and called as 1) Line side and 2) Exchange side.
All the pairs of all those UG cables are terminated on line side of the MDF and given a number to
each pair termination and called as vertical number. 100 pair krone modules are arranged vertically.
Each vertical is numbered individually and each krone module is also numbered. Example :- for
vertical number 2-6-55, 2 says 2nd
vertical, 6 says 6th
module from the bottom of 2nd
vertical and 55
says the pair number in the 6th
module of 2nd
vertical.
Those pairs coming from the exchange switch are terminated on Exchange side of the MDF and
given a number to each pair termination and called as TEN (Terminal Equipment Number). The TEN
is decided by the exchange. 64 pair krone modules are used on this side.
Ex; - Suppose 3-1-4-17-8 TEN indicates the pair is terminated on exchange as 3rd
BM, 1st
rack, 4th
frame, 17th
slot and 8th
port. The same names are written on MDF exchange side.
TELEPHONE EXCHANGE
Telephone is a system of communication in which the individuals called the
subscriber will be able to speak with one and other. It is two way communications. This is requires
conversion of sound energy into electrical energy and at the distant end converting the electrical
energy into sound energy.
The basic requirements of telephones are:
1. Transmitter
2. Receiver
3. Pair of conductor
In addition to the above basic requirements, we require a signalling system that provides a
signal from calling subscriber to exchange and from exchange to called subscriber. From this time we
are using Electronic exchange. Electronic exchange employs space division switching that provides

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one physical path for only one call. Further research resulted in development of time division
switching, which enable to sharing a single path of several calls.
In telephone conversion, the one whom initiate a call, is referred as calling subscriber and the
one for whom the call is referred as called subscriber.
In March 1876 Alexander Graham Bell demonstrated this telephone set and the possibility of
telephony i.e. long distance voice transmission.
The primary purpose of exchange is to provide temporary path for simultaneous bi directional
transmission of speech between
 Subscriber lines are connected to the same exchange ( Local switching)
 Subscriber lines and trunks are connected to other exchange (Outgoing trunk call)
 Subscriber lines and trunks from other exchange(Incoming trunk call)
 Pair of trunks towards different exchanges. (Transit switching)
 Exchange of information with external environment i.e. signalling
 Processing of signalling information and controlling the operation of switching
network.
 Charging and billing.
Types of Switching System
1) Manual
2) Automatic
1) Electromaechanical
a) Strowger (or) Step by step
b) Cross bar
2) Electronic (SPC- Stored program control)
a) Space division switching
b) Time division switching
1) Digital switching
A) Space switch
B) Time switch
C) Combination switch
2 ) Analog switching
Strowger Switch: the control in a strowger system is performed by circuits associated with the
switching elements in the system.
Cross bar System: It has hard wired control sub system which uses relays and latches. No additional
facilities can be provided in these systems.
Electronic Exchange: The control functions are performed by a computer of SPC (stored program
control). New facilities can be provided in this type of switching.
Space division switching:
A dedicated path is established between the calling and called subscribers for the entire duration of
call. It uses in Strowger and crass bar switching systems

21
Time division switching:
The sample values of speech signals are transferred at fixed intervals.
a) Analog: Sampled voltage levels are transmitted.
b) Digital: they are binary coded and transmitted.
1) Space switching: If those coded values send in same time intervals.
2) Time switching: If those values stored and send later time intervals.
3) Space and Time switch: If uses both as combination.
Telephone:
A telephone, or phone, is a telecommunications device that permits two or more users to conduct a
conversation when they are not in the same vicinity of each other to be heard directly. A telephone
converts sound, typically and most efficiently the human voice, into electronic signals suitable
for transmission via cables or other transmission media over long distances, and replays such signals
simultaneously in audible form to its user.
Types of Telephone:
In olden days Decadic dial type of instruments which are having round shaped trigger dial are used.
They are working only for pulse dialling.
But now days EPBT (Electronic Push Button Type) which are having two facilities of pulse and DTMF
dialling are using. DTMF stands for Dual Tone Multi Frequency.
Each subscriber telephone is connected to the exchange by a single twisted copper pair.
 The wires are twisted to help cancel the magnetic fields and thus reduce the interference
between circuits in the same cable.
Functions of local loop:
1) It carries voice signals both ways.
2) It must also carry signalling information in both ways such as dialling pulses or tones from
subscriber to exchange and dial tones, ringing busy signals and pre-recorded messages from
the exchange to subscriber.
3) It must transmit power from exchange to telephone to operate and ring bell.
Signalling
Various Signals:
1) Dc signal:
When ON-hook –DC-Open.
When OFF Hook-48v DC shorted to telephone has 200ohms (approx) when
off hook .so it allows corresponding current. approx 20-80Ma.
2) Dial tone:
When ever lifts the receiver the exchange proceeds by transmitting a dial
tone which consists of 350HZ and 440HZ added together.
3) Dialling :
i)Pulse dialling :-The old type rotary dial phone functions by breaking the loop current
at a 10HZ rate, with a number of interruptions equal to the number dialled .That is dialling digit 4
causes 4 interruptions or 4 pulses in the loop current.
ii) DTMF dialling: Move efficient way for the phone to transmit a combination of two-
tone for each digit.

22
Frequency (HZ) 1209 1336 1477 1633
697 1 2 3 A
770 4 5 6 B
852 7 8 9 C
941 * 0 # D
4) Ringing signal:
When a calling subscriber dials the called number, if the number is free, then the
exchange sends a ringing a ringing signals to called one. The standard ringing voltage from exchange
100 V AC at 20Hz super imposed on 48VDC.
The voltage available at the telephone is less than this due to loop R.
5) Ring back signal:-
When the called telephone is ringing, the exchange sends a pulsed AC
voltage called ring back tone to the calling telephone.
440HZ+480HZ added together.
When called subscriber lifts the phone and then circuit will complete and ring voltages are
switched off and conversation on begins
6) Busy or engage signal:
480 Hz + 620 Hz pulsed signals added together.
Three forms of signalling:-
1. Subscriber loop signalling.
2. Intra exchange-within the exchange and depends on type.
3. Inter exchange-exchange to exchange with common control subsystem.
Various signalling techniques:
Signalling
In Channel Common Channel
Associated Non Associated
DC Low frequency Voice frequency PCM
In band Out band
In band: Vice frequency(VF) Signalling may be Inband or Outband.

23
Voice frequency -> 300Hz to 3400 Hz.
In band means – within the voice band.
Disadvantages: It must be protected against false operation by speech.
Advantages: Important advantage is control signals can be reach to every part where as speech
signals can reach.
It is also independent of transmission systems as the signals would be carried along the route like
the speech signals.
Even A/D and D/A conversion process do not affect them.
So In band signalling is the most widely applied signalling system presently in the long distance
communication networks.
Ex: DTMF tones, dial tone, busy tone, ring back tones
Out Band Signalling: Uses frequencies above voice band but below the upper limit of 4000Hz of the
nominal voice channel spacing.
Advantages: Signalling during the speech period is possible. Thus it will allow continuous supervision
and control of call.
Disadvantage: Only narrow bandwidth is available for signalling. So signalling is required to handle
the signalling band. So it is not widely used. Ex: OFF hook, ON hook DC current.
SS7 Signalling: It is a PSDN (Public Switched data Network). Uses completely separate data
channel to transmit control information between switching systems.
 This reduces the unauthorised entry since users have no access to the control channel and
allows a call to be set up completely before any voice channels are used.
 The status of the whole network can be known to the control equipment and most efficient
routes for calls can be planned.
 It is also provides service like calling number identification.
 SS7 is linking Exchanges each other, Exchange to long distance switching centres, and to
centralised data bases used for such purposes as call display, credit card identification, voice
mail and cellular and PCs telephone roaming information.
 SS7 allows much more data to be sent quickly and with less interference with voice
channels.
 SS7 uses dedicated 64 kbps data channels. Usually one digital voice channels in each
direction is reassigned for this purpose. If necessary an anolog channel with modems can be
used.
 One 64 kbps signalling channel can handle the signalling requirement of many voice
channels.
 With SS7 calls can be set up with no need to tie up a long distance voice channel until the
connection is made.
 But it is necessary to the local exchange to tie up a voice connection from the subs to
exchange because of analog loop cannot support SS7.
 Specific attention has given to the requirement of ISDN while designing SS7. The internal
control and network intelligence essential to ISDN are provided be SS7.
 Although SS7 is suitable for analog & less than 64 kbps channels, it is primarily optimized to
work with digital SPC exchanges utilizing 64kbps digital channels.
 SS7 is suitable for operation over both terrestrial and satellite links.

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Long distance switch Voice ckts/ data ckts
C-DOT DSS MAX
C-DOT DSS MAX is a universal digital switch which can be configured for different applications as
local, transit, or integrated local and transit switch.
High traffic/load handling capacity up to 8,00,000 BHCA with termination capacity of 40,000 Lines
as Local Exchange or 15,000 trunks as Trunk Automatic Exchange.
BASIC BUILDING MODULES
Base Module
Central Module
Administrative Module
Input Output Module
SS7 PSDN
Ex
Ex
Ex
TAX

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The Base Module (BM)
The basic growth unit of the system.
It interfaces the external world to the switch.
The interfaces may be subscriber lines, analogue and digital trunks.
Each Base Module can interface upto 2024 terminations.
It carries out majority of call processing functions
The Single Base Module (SBM)
• In Single Base Module (SBM) exchange configuration, the Base Module acts as an
independent switching system and provides connections to 1500 lines and 128 trunks.
• In such a configuration, the Base Module directly interfaces with the Input Output Module.
• It is a very useful application for small urban and rural environments.
• With minimum modifications in hardware a Base Module (BM) can be remotely located as a
Remote Switch Unit (RSU), parented to the main exchange using PCM links.
Central Module (CM)
• It consists of a message switch and a space switch to provide inter-module communication
• It performs voice and data switching between Base Modules.
• It communicates with Administrative Module for operation and maintenance functions.
• It also provides clock and synchronization on a centralized basis.
Administrative Module
• It support administration and maintenance functions
• It communicates with the Base Module via the Central Module.
• It supports the Input Output Module for providing man- machine interface.
• It also supports the Alarm Display Panel for the audio-visual indication of faults in the
system.
Input Output Module (IOM)
It is a powerful duplex computer system
It interfaces various secondary storage devices like disk drives, cartridge tape drive and floppy drive.
It supports printers and ports for video display units which are used for man- machine
communication interface.
REMOTE SWITCH UNIT
• The normal BM can be modified for remoting with the host exchange via 2 Mbps digital
links.
• The number of 2 Mbps links between the Main Exchange and RSU is primarily determined
by the traffic.
• Operation and maintenance functions are handled by the host exchange.
• A maximum 16 RSUs are possible in C-DOT DSS MAX-XL and 8 RSUs in MAX-L.
BASE MODULE (BM)
The subscribers may be individual or grouped PBX lines, analog or digital lines.
The trunks may be:-
1 Two Wire Physical
2 E&M Four Wire
3 E&M Two Wire
4 Digital CAS or CCS.

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• BASE MODULE (BM)
• The basic functions of a Base Module are –
• Analog to digital conversion of all signals on analog lines and trunks.
• Interface to digital trunks.
• Switching the calls between terminals connected to the same Base Module
• Communication with the Administrative Module via the Central Module for administrative
and maintenance functions
• Provision of special circuits for call processing support e.g. tones, announcements,
MF/DTMF senders/receivers
BASE MODULE (BM) (Contd…)
• Analog Terminal Unit - to interface analog lines/trunks, and providing special circuits as
conference, announcements and terminal tester.
• Digital Terminal Unit - for interfacing digital trunks i.e. 2Mbps E-1/PCM links
• Signaling Unit Module - to support SS7 protocol handlers and call processing functions for
CCS7 calls.
• ISDN Terminal Unit - to support termination of BRI/PRI interfaces
• Time Switch Unit - for voice and message switching and provision of service circuits.
• Base Processor Unit - for control message communication and call processing functions.
Analog Terminal Unit (ATU)
• The Analog Terminal Unit (ATU) is used for interfacing 128 analog terminations which may
be lines or trunks.
• It consists of terminal cards which may be a combination of Line Circuit Cards (LCC), CCB
with Metering (CCM) cards, Two Wire Trunk (TWT) cards, E&M Two wire (EMT) Trunk cards
and E&M Four wire (EMF) trunk cards
• provision to equip Conference (CNF) card
• Announcement (ANN) to support 15 user friendly announcement messages
• Terminal Test Controller (TTC) for testing of analog terminations.
• Power Supply Unit (PSU-I) is used.
Analog Terminal Unit
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Analog Subscriber Line Cards-(terminal cards TC)
• Subscriber line cards as LCC or CCM with interfaces up to 8 subscribers provide basic
BORSCHT functions for each line.
• Each CCM card has the provision of battery reversal for all the 8 lines with the last two lines
having provision to generate 16 KHz metering pulses to be sent to subscriber's metering
equipment.
• Output of four LCCs is multiplexed to form a 32- channel, 2 Mbps PCM link - also called a
terminal group (TG).
Analog Subscriber Line Cards (Contd..)
Since a Terminal Unit has a maximum of 16 terminal cards, there are four such terminal groups.
The signaling information is separated by a scan/drive logic circuit and is sent to the signaling
processor
The LCC/CCM also provides test access relay to isolate the exchange side and line side to test it
separately by using the Terminal Test Controller (TTC).
Analog Trunk Cards
Analog trunk cards interface analog inter-exchange trunks which may be of three types as TWT, EMT
and EMF.
Signaling Processor (SP) Card
• Signaling Processor (SP) processes the signaling information received from the terminal
cards.
• This signaling information consists of scan/drive functions like origination detection, answer
detection, digit reception, reversal detection, etc.
• The validated events are reported to Terminal Interface card.
• Based on the information received from the Terminal Interface Controller, it also drives the
event on the selected terminal through scan/drive signals.
Terminal Interface Controller
(TIC) Card
• Terminal Interface Controller (TIC) controls the four terminal groups (TG) of 32 channels,
• Multiplex them to form a duplicated 128-channel, 8 Mbps link towards the Time Switch (TS).
• For signaling information of 128- channels, it communicates with Signaling Processor (SP) to
receive/send the signaling event on analog terminations.
• Terminal Interface Controller is built around 8-bit microprocessor with associated memory
and interface and it is duplicated for redundancy.
Special Service Cards
• A Terminal Unit has some special service cards such as Conference (CNF) Card.
• Terminal Test Controller (TTC) Card is used to test analog terminal interfaces via the test
access relays on the terminal cards.
• Announcement Controller (ANN) Card provides 15 announcements on broadcast basis.
• Only one service card of each type is equipped in a Base Module with provision of fixed slot
for TTC and variable slots for CNF/ANNC.
• Two slots are occupied by each card i.e. 16 channels for each card are used out of 128
channels available on a Bus between a TU & TS.
Digital Terminal Unit (DTU)
• Digital Terminal Unit (DTU) is used exclusively to interface digital trunks.

28
• One set of Digital Trunk Synchronization (DTS) card along with the Digital Trunk Controller
(DTC) card is used to provide one E-1 interface.
• Each interface occupies one TG of 32 channels and four such interfaces share 4 TGs in a
Digital Terminal Unit.
Digital Terminal Unit
SS7 Signaling Unit Module (SUM)
Any one of the ATU or DTU in a BM can be replaced by SUM frame to support CCS7 signalling.
Only one such unit is equipped in the exchange irrespective of its configuration or capacity.
ss7 Signaling Unit Module
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ISDN - Terminal Unit (ISTU)
• One of the four ATUs/DTUs in a BM can be replaced by ISTU to provide BRI/PRI interfaces in
C-DOT DSS.
• The only constraint is that ISTU has to be principal TU i.e. directly connected to TSU on 8
Mbps PCM link.
• By equipping one ISTU in the exchange, a max. of 256 B channels are available to the
administrator which can be configured as BRI, PRI or any mix as per site requirement.
• Depending on the requirement of number of ISDN-Interfaces, one or more ISTUs can be
integrated in C-DOT DSS, either in one BM or distributed across different BMs.
ISDN Terminal Unit
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Time Switch Unit (TSU)
• Time Switch Unit (TSU) implements three basic functions
• As time switching within the Base Module, routing of control-messages within the Base
Module and across Base Modules and support services like MF/DTMF circuits, answering
circuits, tones, etc.
• These functions are performed by three different functional units, integrated as time switch
unit in a single frame.
Time Switch Unit
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(1) Service Unit (SU)
Service Unit is integrated around three different cards as Tone Generator with Answering Circuit
(TGA), Service Circuit Interface Controller (SCIC) and MF/DTMF Controller (MFC) Card.
Two MFC cards are grouped to form a terminal group.
Up to four MFC Cards can be equipped
(2) Base Message Switch (BMS)
Base Message Switch (BMS) routes the control messages within the Base Module, across different
Base Modules, and also Administrative Module via the Central Module.
It is implemented around two different cards as Message Switch Controller (MSC) with six direct
HDLC-links and the Message Switch Device (MSD) Card implementing 16 switched HDLC links.
As a unit, total 22 HDLC channels are implemented for communication with the Base Processor
(2) Base Message Switch (BMS)
To support 8,00,000 BHCA, MSC and MSD cards are replaced by a High performance Message Switch
(HMS) with high speed, 32 bit microprocessor (MC 68040).
It implements 38 HDLC links
(3) Time Switch (TS)
• The Time Switch complex is implemented using three different functional cards as
multiplexer/demultiplexer (TSM), time switch (TSS) and time switch controller (TSC).
• The Time Switch complex receives the following PCM links and performs time- switching on
them for switching within the Base Module :
• (1) Four 128-channel multiplexed links from four different Terminal Units which may be
any combination of ATU, DTU, #7SU and ISTU.
• . (2) One 128-channel multiplexed BUS from the Service Circuits Interface Controller
(SCIC) in the Time Switch Unit.
• . (3) Three 128-channel links to support onboard three party conference circuits (3 x
128).
Base Processor Unit (BPU)
Base Processor Unit (BPU) is the master controller in the Base Module.
It is implemented as a duplicated controller with memory units.
These duplicated sub-units are realized in the form of the following cards :
Base Processor Controller (BPC) Card
Base Memory Extender (BME) Card
Base Processor Unit
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Base Processor Unit (BPU)
(Contd…)
• BPC controls time-switching within the Base Module via the Base Message Switch and the
Time Switch Controller.
• It communicates with the Administrative Processor via Base Message Switch for operations
and maintenance functions.
• In a SBM configuration, BPC directly interfaces with the Alarm Display Panel and the Input
Output Module.
•
• To support 8,00,000 BHCA, the BPC card is replaced by High performance Processor Card
(HPC).
CENTRAL MODULE (CM)
Central Module (CM) is responsible for space switching of inter-Base Module calls, communication
between Base Modules and the Administrative Module, clock distribution and network
synchronisation.
For these functions, Central Module has a Space Switch, Space Switch Controller and a Central
Message Switch.
CENTRAL MODULE (CM)
(Contd…)
CM provides connectivity to 16 BMs if it is CM-L and 32 BMs if it is CM-XL. Each BM interfaces with
CM via two 512-channel parallel buses as BUS-0 and BUS-1, each operating at 4 Mbps.
In a 32 Base Module configuration, there are 64 parallel buses carrying the voice information from
Base Modules to the Central Module, and also the switched information in the reverse direction.
Space Switch (SS) and Space Switch Controller (SSC)
In order to take care of the large number of interface signals, the switch portion of CM is divided into
three stages viz. MUX stage, Switch stage and DEMUX stage.
The MUX and DEMUX stages are implemented on single card to provide the Base Module to Central
Module interface in each direction.
SS and SSC (contd..)
Interfacing and switching are controlled by SSC which provides control signals for the MUX/DEMUX
cards and the Space Switch Switch cards.
These time-slots carry control message from each Base Module and these messages are sent to the
Central Message Switch (CMS).
Clock Distribution
• CM provides the central clock for distribution to the Base Modules.
• The 8MHz clock may be locally generated at the Central Clock (CCK) card in case of CM-XL
and of Space Switch Clock (SCK) card in case of CM-L by using high stability VCXO crystal
• or may be derived from an external reference clock using the Network Synchronisation
Controller (NSC) card in case of CM-XL and Network Synchronisation Equipment (NSE) in
case CM-L under the control of SSC.

32
NETWORK SYNCHRONIZATION
IN C-DOT DSS
Locked Mode
Holdover Mode
Free Run Mode
Central Message Switch (CMS)
. It is implemented as four different message switches, working in load-sharing mode.
Each message switch is a high performance message routing block, implemented by using high speed
32 bit microprocessor MC 68040 in case of CM-XL and 16 bit microprocessor MC 68000 in case of
CM L.
ADMINISTRATIVE MODULE (AM)
• Administrative Module (AM) consists of a duplicated 16/32-bit controller called the
Administrative Processor (APC).
• It communicates with Base Processors via the Central Message Switch for control messages
and with the duplicated Input Output Processors in the Input Output Module for interfacing
peripheral devices
• Administrative processor is responsible for global routing, translation, resource allocation
and all other functions that are provided centrally in C-DOT DSS MAX
INPUT OUTPUT MODULE (IOM)
• Input Output Module (IOM) consists of duplicated Input Output Processor (IOP).
• The Input Output Processor (IOP) is a general purpose computer with UNIX Operating
System.
• It is used as the front end processor in C-DOT DSS.
• It handles all the input and output functions in C-DOT DSS.
• The IOP is connected to AP/BP via HDLC links
IOP-VH Hardware Architecture
• The IOP-VH is value engineered high performance IOP, designed using a single card.
• The IOP CPU uses MC 68040 (25 MHz) processor on the VHC card.
• All active IOP processes reside in the dynamic RAM.
• Also the data being transferred through HDLC links, secondary storage devices and
terminals, use the dynamic RAM.
• The IOP as a module is duplicated to provide redundancy for cartridge and disk drives as well
as serial communication terminals and printers..
• Presently the two ports, namely X.25 and ETHERNET are not supported in current UNIX
release.
IOP-VH Peripherals
Input Output Processor (IOP-VH) supports three standard SCSI-2 interfaces, on VHC card,
one each for Winchester Drive, Cartridge Tape Drive and one as spare.
Here, it may be noted that only the peripherals with SCSI-2 interface can be used in IOP-VH.
Front Panel Display
• The CPU ‘Reset’ and ‘Abort’ switches are provided along with lock and key.
• ‘Run’ and ‘Halt’ LEDs for the CPU status indication is also extended on the front panel.
• A ‘Reset’ LED is provided along with RESET switch and glows when the CPU is reset by
pressing ‘RESET’ switch on the front panel.
• Power I/P LED is provided to indicate the presence of I/P power on the front panel.

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REMOTE SWITCHING UNIT (RSU)
In case of a Remote Switch Unit (RSU) the Time Switch Switch (TSS) cards in BM are replaced by
Enhanced Time Switch (ETS) cards.
In case of a remotely located BM (RSU), the corresponding MUX/DEMUX cards in CM are replaced
by Enhanced Switch MUX (ESM) Cards in CM-XL and ESL cards in CM-L.
ALARM DISPLAY PANEL
• It is a three card implementation. A matrix of LEDs is provided to indicate the maintenance
status of the switch units and their level of initialization.
• A seven-segment display shows the count of lines and trunks currently faulty.
• Keys are provided for manual acknowledgment, initiating self test and selective audio
disable.
C-DOT AN-RAX: (Access Network Rural Automatic Exchange)
For connecting rural area subscribers of KODAD MBM (The subscriber areas beyond 7 km
and above from the KODAD MBM) CDOT ANRAX exchanges were installed at various villages around
KODAD. There were 21 ANRAX exchanges installed and connected directly to the KODAD MBM
exchange and each exchange is capable for serve 248 subscribers in that area. For running the
ANRAX the power supply purpose battery sets, power plant, and engine alternator were also
installed at those premises. Broadband DSLAMs and Cell BTSs also installed at various ANRAXs.
INTRODUCTION
The product AN-RAX is basically a Subscriber line concentrator, used for remoting. There are
three level of remoting, namely the first, second and third level, from the 'Local Exchange' (LE)
(Fig.shown below).
The 'Remote Switch Unit' (RSU) provides the functionality of first level of remoting. All the
Subscribers connected to RSU can access each other and also the subscribers, in the 'National
Network' (NAT-NW), through LE. RSU in this case will, perform the functionality of a complete switch
(with both intra exchange and upto NAT-NW Switching). It will handle the 'Call Processing' (CP),
charging and billing functionality, but would itself be a part of the LE.
RSU can also provide concentration.
The ‘C-DOT Access Network - RAX ’ (AN-RAX) will provide the second level of remoting. AN-
RAX might be connected to a RSU or directly to the LE. The AN-RAX supports V5.2 protocol, and
handles the functionality of second level of remoting.
The second level of remoting has its scope and role clearly defined. At this level there would
neither be any intra switching or call processing activities, nor the AN-RAX would handle the
charging, billing and administration functions of subscribers.
AN-RAX provides a transparent link between the subscriber and LE. It handles the various
subscriber events, the BORSCHT functionalities. (Battery feed, Over voltage protection, Ringing,
Supervision, Coding, Hybrid and Testing).
All the administration, call processing, charging, billing, traffic monitoring and switching are
performed at LE, where AN-RAX plays the role of front end termination at remote end.
The main feature of AN-RAX is that it provides concentration, through V 5.2 protocol, which
is used as a signalling protocol between LE and AN-RAX. 248 PSTN subscribers can be supported on
two E1 links towards LE, thus providing an approximate concentration of 4:1. This places the AN-RAX
at a level higher than a simple MUX, which is used at third level of remoting. The system can work on
one E1 link towards LE, but without ‘PROTECTION’, resulting in increase in concentration to 8:1.
Third Level of remoting handles the front end functions (subscriber events), but does not
provide any concentration. The various subscriber ports of MUX have nailed up (fixed) slots in the
link towards LE. The MUX may be connected directly to LE or to an unit of a higher level of remoting.

34
ANRAX HARDWARE ARCHITECTURE The integrated circuits used in the C-DOT 256P AN-RAX
hardware have low power dissipation and high operational reliability. The components used are
based on Metal-Oxide Semiconductor (MOS), Complementary MOS (CMOS), Low-Power Schottky
Transistor-Transistor Logic (LSTTL), and bipolar technologies. All the system circuitry has been
packaged into seven card types. On the broad level these could be divided into following categories:
 Terminal Interfaces
 Subscriber Line Card (LCC/CCM)
 Controller Cards
 AN-RAX Controller Card (ARC)
 AN-RAX Interface Card (ARI)
 Signalling Processor Card (SPC) or Integrated Signalling Processor Card (ISP)
 Service Cards
 RAX Terminal Tester Card (RTC)
 Power Supply Unit (PSU-I)

35

36
FEATURES OF ANRAX
 Provides front end termination for PSTN subscribers
 Supports maximum of 248 PSTN subscribers
 Connected to Local Exchange (LE) over one or two E1 links using standard V5.2 Protocol as
per ITU-T specifications G.964 & G.965 and ETSI specifications 300-324 & 300-347.
 Provides First/Second Level of remoting
 Provides a transparent link between subscriber and Local Exchange
 Provides Calling Line Identification Presentation (CLIP) on 2 ports of LCC card
 Provides 16KHz Metering Pulse and Calling Line Identification Presentation (CLIP) on 2 ports
of each CCM card
 Provides Reversal on all 8 ports of CCM card
 Provides Man Machine Interface (MMI) using VT-100 dumb terminal
 Password Protection
 Requires no air-conditioning
 Low Power Consumption
 Line Testing can be performed locally
 Transparently supports all subscribers feature as supported by Local Exchange (LE)
 For any feature related enhancements, the S/W changes are to be done on Local Exchange
(LE) only
Consists of two controller cards
 AN RAX Controller Card (ARC Card)
 AN RAX Interface Card (ARI Card)
ARC card supports 2 E1 links toward Local Exchange
Both the cards form a security block along with respective SPC cards
Redundancy in Controller Cards
8 port LCC/CCM cards for Subscriber Interface
RTC card for testing of subscriber ports
DIFFERENCE BETWEEN
C-DOT RSU AND C-DOT AN-RAX
C-DOT RSU C-DOT AN-RAX
 First Level of Remoting  First/Second Level of
Remoting
 Connected to LE through
Proprietory Protocol
 Connected to LE through
Standard V5 protocol
 In standalone mode it performs
the various call processing &
Billing functions
 In standalone mode it only
feeds the tone/ announcement
to the subscriber

37
RSU OF CDOT
INTRODUCTION
RSU is a remote unit of a geographically distributed exchange being controlled by the parent
exchange and also has the capability for local switching.
It is an independent unit of a large exchange capable of performing all the functions
associated with an exchange. All operation & maintenance activities related to RSU can be
performed from the parent exchange.
a) The space / area requirement for large exchanges (say 40K) is quite high and it is not
always possible to find such a site in the already congested metros. Instead of one
large monolithic area a number of small areas are provided to install such
exchanges. In such a case the solution is RSU.
b) In our country there is a need for small exchanges in many places. These may be
nearby stations but it is not economical to extend cable pairs from large telephone
exchanges to all the subscribers in these places. One solution is to install small
capacity exchange and interconnect them via trunks. However from network
planning point of view and ease of operation & maintenance, it would be preferable
if we can have an exchange which is distributed over these places.
c) The RSU can also be used to interconnect a group of RAXs in nearby villages thus
saving the cable costs needed to interconnect RAXs and reducing the network
complexity.
C-DOT DSS MAX is a modular and flexible digital switching system which provides
economical means of serving metropolitan, urban and rural environments. The system
employs an open ended architecture for flexibility of configuration and growth. The Remote
Switch Unit (RSU) is an addendum to the C-DOT DSS Family of switches. Similar to existing C-
DOT DSS Products, its architecture is characterized by distributed control and message based
communication in order to achieve a loosely coupled network in a flexible system
architecture.
Software is distributed over various processors and is packaged such that depending upon
the actual switch configuration; it can be distributed over appropriate controllers. Some
initialization strategies are changed in the Remote Switch Software keeping in view the need
of working of the RSU in standalone configuration for local switching capability. Data bases
are modified accordingly.
Mostly the message communication between processors distributed all over the exchanges is via
HDLC links. Here, an important change has taken place as far as communication between the
Remote Base Module and the Central Module is concerned where the media is PCM Cable
instead of the 10 bit parallel bus existing in the case of communication between collocated BM
and the Central Module.
1.2 Basic Modules
C-DOT DSS MAX exchanges can be configured from five basic modules (Fig 11.1)
a. Remote Base Module
b. Collocated Base Module
c. Central Module

38
d. Administrative Module
e. Input Output Module
TAX (Trunk Automatic Exchange) or Tandem Office
d) A telephone central office switch that links telecom end offices together and does not
connect to the customer directly. Also called a "Class 4 switch" or "TDM switch," a tandem
switch is a computer that is specialized for TDM-based, circuit-switched telephone calls.
e) All the trunks of KODAD MBM are connected to the TAX which is situated at Nalgonda town.
All the STD calls routed to the TAX using CCS& signalling system. For CCS&7 signalling system
a frame called SUM was installed in 2nd
BM of KODAD MBM.
f) Now the TAX system also converted to the IPTAX which is working in the IP based network.
Those IPTAX switches are located at Chennai and Hyderabad.
ISDN
CCITT: consultative committee for international Telephony & telegraphy.
PRINCIPLES OF ISDN: -
 Should support voice and non-voice in same network.
 Should support variety of applications with switched or non-switched connections.
 Whenever introduce new service it should compatible with 64kbps digital
connection.
 ISDN will contain intelligence.
ISDN ARCHITECTURE:-
 ISDN supports
Digital subscriber loop
Variety of transmission services
DTE-DCE INTERFACE:
 DTE-data terminal equipment
 DCE- data circuit terminating equipment
In ISDN single interface will be used for telephones, computers &video.
So various protocols required to allow control information.
3basic types of channels available with ISDN.
B channel: 64kbps
D channel: 16 or 64 kbps
H channel: 384, 1536 or 1920 kbps
B&D are compatible with DS1 to DS4.
BRI (Basic rate interface):-
 BRI subs access consisting of 3 no.s full duplex, time division multiplexed digital channels.
 One B- channel for digitally encoded voice.
 Another B- channel for applications such as data transmission, PCM encoded digitalized
voice, vediotex
 One D -channel for signalling & network control information.
So BRI requires 2 no of B channels i.e. 128kbps
1 no of D channel 16kbps
Framing, synchronisation and other over head bits i.e. 48kbps total – 192kbps.
H channel are provided for higher bit rates such as fast facsimile, video, high speed data.

39
PRI (Primary access or primary rate interface):
There is another service called the primary service, primary rate interface (PRI) that will provide
multiple 64KBPS channels intended to be used by the higher volume subscriber to the network. in
the united states, Canada, Japan and Korea , the primary rate interface consists of 23 64Kbps b-
channel and one 64Kbps d-channel (23b+d) for a combined bit rate of 1.544MBPS. In Europe the
PRI uses thirty 64KBPS b-channel and one 64Kbps d-channel for a combined bit rate at 2.048Mbps.
ISDN will support variety of service including the exiting voice and data services and a host new
service.
A short list of source of the important new services is:
1. Video
2. Electronic mail
3. Digital facsimile
4. Tele text
5. Data base access
6. Electronic file transfer
7. Image and graphics exchange
8. Document storage and transfer
9. Automatic alarm
10. Audio and video conferencing.
In Kodad BSNL C-DOT MBM EXCHANGE one frame for ISDN is a equipped separately in 2nd
BM. 1
frame means we can give 128 no. of subscribers ISDN connection mainly in Kodad ISDN connections
is using for banks and other commercial offices as only stand by connection for the existing Leased
line connection. Whenever leased line data connection failed the data will be changed to ISDN
automatically and bank will be working. ISDN BRI type connection using as stand by only due to high
splitter billing cost than existing leased line and data bit rate is also slow.
BSNL BROADBAND:
It is a brand name of internet connection provided by BSNL over existing land line. Actually
Broadband means Internet access connection with a minimum speed of 256 kbps.
BSNL Broadband is an Internet access service from state-owned Bharat Sanchar Nigam Limited (BSNL)
available in India since 14 January 2005. Until 30 September 2007 it was known as Data One.[1]
BSNL is commissioning[when?]
a multi-gigabit, multi-protocol, IP infrastructure through National Internet
Backbone-II (NIB-II), that will provide services through the same backbone and broadband access
network. The broadband service will be available on digital subscriber line technology (on the same wire
that is used for plain old telephone service.
NIB-II would have put India at par with more advanced nations. The services that would be supported
include always-on broadband access to the Internet for residential and business customers, content-
based services, video multicasting, video-on-demand and interactive gaming, audio and video
conferencing, IP telephony, distance learning, messaging, multi-site MPLS VPNs with Quality of Service
(QoS) guarantees. The subscribers would have been able to access the above services through Subscriber
Service Selection System (SSSS) portal.

40
The service will be given through Multi Protocol Label Switching (MPLS) based IP infrastructure. Layer 1 of
the network will consist of a high-speed backbone composed of 24 core routers connected with high-
speed 2.0 Gbit/s(STM-16) links.

41
ADSL
DSL is a Data communication Technology that enables high speed data transmission over
existing copper telephone wires from exchange to subscriber.
By using DSL Technology BSNL providing high speed broadband
service over the existing copper pairs from exchange to the subscriber homes or offices.
In BSNL Exchange there is an equipment DSLAM was installed for
providing broadband over copper pair. The pairs coming out from DALAM is called DSL
wires(having frequency range 25khz to 1.1mhz) and the wires coming from exchange
output(having frequency range 0 to 4khz) for voice calls are combined together at exchange
output(i e in MDF) and sent to outdoor copper pair. The same copper pair was terminated at
subscribers end and separated by a frequency filter called splitter. It gives 0 to 4khz voice
frequency to phone and 25khz to 1.1mhz frequency output to an ADSL modem.
Hence the phone and broadband may use at a time without any interruption.
DSL types are,
SDSL-Symmetric DSL
ADSL-Asymmetric DSL
VDSL-Very high speed DSL
SDSL means it provides same speeds for download and upload streams.
So upload bandwidth allotted and equipped same as to download bandwidth. So SDSL is
uneconomical due to subscribers are using download data in higher amount compared to
upload data.
ADSL technology provides high download stream bandwidth and low
upload stream bandwidth. So in subscribers and equipment point of view the ADSL
technologies are as follows.
ADSL variant Max up/downstream rate Max local loop strength
ADSL 1Mbps/10Mbps 5.5km
ADSL lite 384Kbps/1.5Mbps 5.5km
ADSL 2 1mbps/12Mbps 5.5km
ADSL 2+ 1Mbps/20Mbps 5.5km
ADSL 2++ 52Mbps(max)and in developing
stage
Developing
Hence we can provide broadband up to 5.5km with up/down stream rates
1Mbps/20Mbps using ADSL 2+ Technology and BSNL presently using this technology and
providing 450 broadband connections in KODAD town and 300 broadband connections in
KODAD rural areas.

42
ADSL MODEM
This is modulator and demodulator which is used for ADSL technology. It is connected to the
DSLAM at exchange premises via land line.
A digital subscriber line (DSL) modem is a device used to connect a computer or router to a
telephone line which provides the digital subscriber line service for connectivity to the Internet, which is
often called DSL broadband.
The more common DSL router which combines the function of a DSL modem and a home router, is
a standalone device which can be connected to multiple computers through multiple Ethernet ports or an
integral wireless access point. Also called a residential gateway, a DSL router usually manages the
connection and sharing of the DSL service in a home or small office network.
A DSL router consists of a box which has an RJ11 jack to connect to a standard subscriber
telephone line. It has several RJ45 jacks for Ethernet cables to connect it to computers or printers,
creating a local network. It usually also has a USB jack which can be used to connect to computers via
a USB cable, to allow connection to computers without an Ethernet port. A wireless DSL router also has
antennas to allow it to act as a wireless access point, so computers can connect to it forming a wireless
network. Power is usually supplied by a cord from a wall wart transformer.
It usually has a series of LED status lights which show the status of parts of the DSL communications link:
 Power light - indicates that the modem is turned on and has power.
 Ethernet lights - There is usually a light over each Ethernet jack. A steady (or sometimes flashing)
light indicates that the Ethernet link to that computer or device is functioning
 DSL light - a steady light indicates that the modem has established contact with the equipment in the
local telephone exchange (DSLAM) so the DSL link over the telephone line is functioning
 Internet light - a steady light indicates that the IP address and DHCP protocol are initialized and
working, so the system is connected to the Internet
 Wireless light - only in wireless DSL modems, this indicates that the wireless network is initialized
and working
Many routers provide an internal web page to the local network for device configuration and status
reporting. Most DSL routers are designed to be installed by the customer for which a CD or DVD
containing an installation program is supplied. The program may also activate the DSL service. Upon
powering the router it may take several minutes for the local network and DSL link to initialize, usually
indicated by the status lights turning green.
Apart from connecting to a DSL service, many modems offer additional integrated features, forming
a residential gateway:
 ADSL2 or ADSL2+ support
 Router functionality that includes Network Address Translation (NAT) to share a single IPv4 address.
 An 802.11b, 802.11g or 802.11n wireless access point
 A built-in switch (typically 4 ports)
 Virtual Private Network termination
 Dynamic Host Configuration Protocol (DHCP) server
 Dynamic DNS (Domain Name System) clients

43
 Voice over Internet Protocol functionality including Quality of Service (priority control for data flows
between users)
At KODAD mainly 2 types of modems are used. These are
TYPES LAN PORTS USB port WI-FI
Type-1 1 1 Not available
Type 2 4 - Available
So many manufactures are available like TERACOM, UT STARCOM, ITI.NOKIA SEIMENS,
VMC, ZTE etc.
ADSL modems consist of following light indication. There are
1. Power light 2.DSL/LINK/ADSL 3.INTERNET/INET 4.LAN/ETHERNET 5.USB/PC
The ADSL modems can configured in two modes
1) PPPOE MODE: This is also known as “Always ON” mode. PPPOE means Point to Point Protocol
Over Ethernet. Simply the user name and password are to be entered and save in the modem
configuration. If the DSL light is stable in the modem, it will automatically dialled and connected to
the Internet and the Internet is available up to the modem, without any necessity of computer. The
Internet light on the modem indicates the status of the Internet. If it turns into blue the internet is
available up to the modem, if turns red means the Internet is not connected and this may be due to
some problem or error. Due to there is no necessity of computer, PPPOE mode does not shows
errors and their numbers.
2) BRIDGE MODE: In this mode of configuration the modem just bridges the connection from PC to
Internet. A dial up connection has to be created in the Computer and connect when ever required by
using those Username and Password which is provided by BSNL. Hence Internet is only available to
the PC which is connected using Broadband connection. So this mode of connection is used to single
user. If there is any problem in connecting broadband the PC shows the corresponding error with an
error number.
TROUBLE SHOOTING IN Broadband connection:
The commonly shown errors in OS of windows 7/8, windows XP errors are 678/651 or 691 or
769 or 676.
1. Error 678/651: Whenever any connectivity problem between PC and Internet Gateway
TO CHECK THE ERRORS;
a. Check dial tone in the phone
b. Check DSL light: DSL indicates connectivity from Broad band modem to DSLAM.
It should be glow constant (fixed) should not blink. The Landline copper pair is the key element in
connecting from ADSL modem to the DSLAM. Verify splitter connections proper or not. Then verify
drop wire for any loose connections or any dry joints. And then test the landline for any faults.
c. Check LAN card properly connected or not.
d. Check internet status up to the DSLAM verify some other broadband connections.
If some are working there is no fault Up to DSLAM.I f all are not working check out the OFC network
from DSLAM to BBRAS.
e. Check PC if it is working properly or not.
f. Reset the modem and configure again
g. Verify connections at splitter if good change the splitter (or)give direct connection
to modem without splitter and phone and then check.

44
h. change port at DSLAM and check the connections it should give 691 error.
2. Error 691:user name and password wrong
To check the errors:
1. Retype the user name and password correctly and connect again.
2. If not connected verify the subscribers was connected in the port which is allotted to
him or not. If not in that port, change to the correct port or a port change request put
up to BBRAS.
3. Verify dial tone if it gives any outgoing announcement like your phone facility is
disconnected. If so pay the telephone bill.
3. Error 769: whenever LAN is disabling in PC it will show 769. So enable the Local area
connection in the pc.
4. Error 676: line is busy
1. One pc already connected, the another pc shows 676.
2. Whenever connection failed by power or something trail immediately will show
676. Wait for some time and try again.
3. Reconfigure the modem.
Preventive Maintenance of Broadband Service.
1) Keep landline in proper manner.
2) A new drop wire should be provided at the time of new broadband connection.
3) Length of the drop wire should be minimum as possible.
4) Should not provide broadband connection after 5.5 km length.
5) Keep the DSLAM and other Broadband equipment like BB modules should be kept dust
free and air conditioned. And avoid all loose connections. Use proper tools.
6) Proper Bandwidth allotment should be done in the OFC network for required speed.
7) BSNL persons should educate the customer to self handle any complaint at Customer
Premises Equipment like splitter connections, creation of connection in PC and
configuration of modem.
DSL
Digital Subscriber Line (DSL) is a broadband access technology that enables high-speed data
transmissions over the existing copper telephone wires (“local loops”) that connect
subscriber’s homes or offices to their local telephone company Central Offices (COs).
Contrary to the analogue modem network access that uses up to 4 kHz signal frequencies on
the telephone wires and is limited to 56Kbps data rates, DSL is able to achieve up to 52Mbps
data transmission rates by using advanced signal modulation technologies in the 25 kHz and
1.1 MHz frequency range.
DSL flavours
There are a number of different DSL standards defined by American National Standards
Institute (ANSI) and European Telecommunications Standards Institute (ETSI) and embraced
by the industry. These DSL technology variants are typically characterized by different
upstream and downstream data rates, maximum wire lengths and designated customer
applications – residential, small office
or business oriented. Collectively, the DSL standards are referred to as xDSL. Roughly, xDSL
standards can be divided into the following three groups:

45
I. Symmetric DSL – provides the same data rate for
Upstream and downstream transmissions and includes the
Following types:
DSL Variant Max Up/Downstream Rate Max local loop wire length
HDSL – High 1.5Mbps/1.5Mbps 3.7 km
Data rate Digital
Subscriber Line
SDSL – Symmetric 2.3Mbps/2.3Mbps 3 km
Digital Subscriber
Line
SHDSL - 4.6Mbps/4.6Mbps 5 km
Symmetric High
Bit rate Digital
Subscriber Line
II. Asymmetric DSL – provides higher downstream then
Upstream data transmission rates and includes the
Following types: DSL Variant Max Up/
Downstream Rate Max local loop wire length
ADSL 1Mbps/10Mbps 5.5km
– Asymmetric
Digital Subscriber
Line
ADSL Lite 384Kbps/1.5Mbps 5.5km
- Asymmetric
Digital Subscriber
Line Lite
ADSL 2 - 1Mbps/12Mbps 5.5km
Asymmetric
ADSL 2+ 1Mbps/20Mbps 5.5km - Presently BSNL being
used.
- Asymmetric
Digital Subscriber
Line 2+
ADSL 2++ 52Mbps over short distances
Developingtechnology
or ADSL 4
- Asymmetric
Digital Subscriber
Line 2++

46
III. Symmetric and Asymmetric DSL – can transmit data
both symmetrically and asymmetrically and includes the
following type:
DSL Variant Max Up/Downstream Rate Max local loop wire length
VDSL – Very High 10Mbps/10Mbps 0.3km – 1.3km
bit rate Digital 1.5Mbps/52Mbps
Subscriber Line
VDSL 2 – Very 100Mbps/100Mbps 0.5 km
High bit rate symmetric
Digital Subscriber
Line
Asymmetric Digital Subscriber Line (ADSL) variants are by far the most popular DSL
implementations mostly due to its suitability for Internet browsing applications that are
heavily geared towards downstream data transmission (download):
DSLAM
When digital data is sent from a DSL subscriber’s premises, it travels from subscriber’s
computer or network through a DSL modem and on to the other end of the line at the
phone company’s Central Office (CO). At the CO end of the line (local loop) the data is
received by the Digital Subscriber Line Access Multiplexer (DSLAM). The DSLAM aggregates
the digital data streams coming from a number of subscribers onto a single high-capacity
uplink (ATM or Gigabit Ethernet backhaul) to the Internet Service Provider. At the ISP the
aggregated data from multiple subscribers is processed by the Broadband Remote Access
Server (B-RAS) which authenticates the subscriber’s credentials, validates the users access
policies and routes the data to its respective destinations on the Internet.
This is an extremely simplistic outline of the DSL access network flow but it carries the
message that what really makes DSL happen are the DSL modems and DSLAM and
B-RAS devices. The following chapters will concentrate on the DSLAM and B-RAS
architecture, functionality and classification as well as mention the performance and
scalability challenges
These devices face in modern Triple-Play networks.
DSLAMs overview
The Digital Subscriber Line Access Multiplexer or DSLAM is the equipment that really allows
the DSL to happen. The DSLAM handles the high-speed digital data streams coming from
numerous subscribers’ DSL modems and aggregates it onto a single high-capacity uplink –
ATM or Gigabit
Ethernet to the Internet Service Provider. Contemporary DSLAMs typically support multiple
DSL
Transmission types – ADSL, SDSL, etc as well as different protocol and modulation
technologies within the same DSL type. Responding to the requirements posed by
broadband

47
Network evolution towards provision of value added services such as VoDSL and IPTV,
modern DSLAMs, in Addition to DSL aggregation functions, begin to provide advanced
functionality such as traffic management, QoS, authentication via DHCP Relay, IGMP
Snooping as well as
in some cases IP routing and security enforcement.
DSLAM architecture
From the high-level perspective ATM DSLAMs, Ethernet DSLAMs and IP-DSLAMs
architecture typically includes a number of xDSL line cards that terminate the subscriber
local loops and one or more ATM OC-3/12/48 or Ethernet/ Gigabit Ethernet uplink cards for
traffic backhaul. The line cards and uplink cards are interconnected by a high capacity
aggregation backplane that can take form of an
ATM or Ethernet bridge or switch. Majority of modern DSLAMs are multiservice and support
multiple DSL technologies – i.e. ADSL, ADSL2, ADSL2+, SDSL and VDSL, etc and therefore
these devices accommodate for multiple xDSL line card types.
BACKPLANE
LI
NE
CA
RD
LIN
E
CA
RD
LIN
E
CAR
D UP LINK ARD

48
BBRAS
A broadband remote access server (BRAS, B-RAS or BBRAS) routes traffic to and from broadband
remote access devices such as digital subscriber line access multiplexers (DSLAM) on an Internet
service provider's (ISP) network. BRAS can also be referred to as a Broadband Network
Gateway(BNG).
The BRAS sits at the core of an ISP's network, and aggregates user sessions from the access network.
It is at the BRAS that an ISP can inject policy management and IP Quality of Service (QoS).
The specific tasks include:Aggregates the circuits from one or more link access devices such
as DSLAMs
 Provides layer 2 connectivity through either transparent bridging or PPP sessions
over Ethernet orATM sessions
 Enforces quality of service (QoS) policies
 Provides layer 3 connectivity and routes IP traffic through an Internet service provider’s
backbone network to the Internet
A DSLAM collects data traffic from multiple subscribers into a centralized point so that it can be
transported to a switch or router over a Frame Relay, ATM, or Ethernet connection.
The router provides the logical network termination. Common link access methods include PPP over
Ethernet (PPPoE), PPP over ATM (PPPoA) encapsulated sessions, bridged ethernet over ATM or
Frame Relay (RFC 1483/RFC 1490), or just plain ethernet. In the case of ATM or Frame Relay based
access, individual subscribers are identified by Virtual Circuit IDs. Subscribers connected over
ethernet-based remote access devices are usually identified by VLAN IDs or MPLS tags. By acting as
the network termination point, the BRAS is responsible for assigning network parameters such as IP
addresses to the clients. The BRAS is also the first IP hop from the client to the Internet.
The BRAS is also the interface to authentication, authorization and accounting systems (see RADIUS).

49
WI-FI (WIRELESS FIDELITY)
6.1 WI-FI NETWORK:
A Wi-Fi network provides the features and benefits of traditional LAN technologies such as
Ethernet and Token Ring without the limitations of wires or cables. It provides the final few meters
of connectivity between a wired network and the mobile user. WIFI is a wireless LAN Technology to
deliver wireless broad band speeds up to 54 Mbps to Laptops, PCs, PDAs, dual mode Wi-Fi enabled
phones etc.
6.2 WORKING OF WI-FI NETWORK:
In a typical Wi-Fi configuration, a transmitter/receiver (transceiver) device, called the Access
Point (AP), connects to the wired network from a fixed location using standard cabling. A wireless
Access Point combines router and bridging functions, it bridges network traffic, usually from
Ethernet to the airwaves, where it routes to computers with wireless adapters. The AP can reside at
any node of the wired network and acts as a gateway for wireless data to be routed onto the wired
network. It supports only 10 to 30 mobile devices per Access Point (AP) depending on the network
traffic. Like a cellular system, the Wi-Fi is capable of roaming from the AP and re-connecting to the
network through another AP. Like a cellular phone system, the wireless LAN is capable of roaming
from the AP and re-connecting to the network through other APs residing at other points on the
wired network. This can allow the wired LAN to be extended to cover a much larger area than the
existing coverage by the use of multiple APs such as in a campus environment. It may be used as a
standalone network anywhere to link multiple computers together without having to build or extend
a wired network.
FIG 6.1WI-FI NETWORK (REF- 5)
End users access the Wi-Fi network through Wi-Fi adapters, which are implemented as cards
in desktop computers, or integrated within hand-held computers. Wi-Fi wireless LAN adapters
provide an interface between the client Network Operating System (NOS) and the airwaves via an
antenna.

50
6.3 BENEFITS OF WI-FI:
Wi-Fi offers the following productivity, conveniences, and cost advantages over traditional wired
networks:
 Mobility: Wi-Fi systems can provide LAN users with access to real-time information anywhere
in their organization.
 Installation Speed and Simplicity: Installing a Wi-Fi system can be fast and easy and can
eliminate the need to pull cable through walls and ceilings.
 Installation Flexibility: Wireless technology allows the network to go where wire cannot go.
 Reduced Cost-of-Ownership: While the initial investment required for Wi-Fi hardware can be
higher than the cost of wired LAN hardware, overall installation expenses and life-cycle costs
can be significantly lower.
 Scalability: Wi-Fi systems can be configured in a variety of topologies to meet the needs of
specific applications and installations. Configurations are easily changed and range from peer-
to-peer networks suitable for a small number of users to full infrastructure networks of
thousands of users that allows roaming over a broad area.
 It offers much high speed up to 54 Mbps which is very much greater than other wireless access
technologies like CORDECT, GSM and CDMA.
Leased Line:
Means Permanent point to point connections
 Ideal for linking two offices
 Always-on, uncontended symmetric data
 Fixed monthly charges
 Quality of Service network guarantee
A leased line is a permanent, always on connection between two locations. It is a dedicated, private
line and only carries communications and traffic from your company, resulting in a guaranteed level
of service. The line can be used for data, video and voice and is most effective when sharing
bandwidth hungry applications between different offices.

51
WHO WOULD BENEFIT FROM A LEASED LINE?
 Companies with separate office locations that regularly share a lot of data
 Companies with separate office locations who want to use VoIP

52

53
WHAT BENEFITS WOULD A LEASED LINE BRING MY BUSINESS?
 Cost effective for heavy Internet users
 High speed data throughput
 Private connection with no contention ratios
 Fixed charges regardless of usage, allowing accurate budgeting
 A guaranteed high level of service with vastly reduced latency and jitter
In Kodad nearly 45 leased lines were provided by BSNL. All the nationalised banks,
Govt. offices like MRO, MPDO, RTA and other private offices like finance offices are using leased
lines for connecting from Kodad local office to their main head quarters offices or their centralized
servers situated at another locations.
For a normal leased line several modems are required at each termination of
network and can be provided for only 64Kbps or 2Mbps speed only. Hence network is complicated
and cannot be monitored centrally.
Multiplexer (MUX)
For a normal 64kbps leased lines one multiplexer is called MUX is provided at the telephone
exchange. One MUX is served for 30 no of 64kbps channels. MUX has 5 terminal cards each can
connect 6 no of 64 kbps channels and corresponding control cards also inserted. One incoming
2mbps E1 channel from Nalgonda is connected to one MUX from there 30 no. of 64 channels comes
out to provide 30 leased line circuits. Each terminal card front end is provided with loop facility for
loop test purpose.
2 Mbps Primary MUX (PDM-30A)
It is a Primary PCM Multiplexer provides flexible modular VLSI based solutions which provide voice &
data applications by TDM on 2,048 MB/s E1 stream. The equipment is fully solid state, field proven
and conforming to ITU-T standards. It is designed to connect 30 subscribers to an Analog or Digital
exchange and multiplexes 30 voice or data or any combination of voice/data channels of 64 Kb/s
into a 2 Mb/s G.703 stream. It is a rugged design equipped with twenty slots for various units. Four
of them are the common units and the remaining sixteen slots are for voice, data & signalling units,
which provides a variety of user services. All the voice/data units are HOT SWAPPABLE and different
types of voice/data units can be placed in to it simultaneously with arbitrary combination.
Features
 TEC "Type Approved" by Department of Telecom (DoT)
 Largest installation base in BSNL network
 Standard CP-7 rack mounting
 Both Voice and Data Applications on E1

54
 Full conformance to ITU-T (standards)
 CCB payphone application with 16 KHz polarity reversal
 Flexible internet working with selectable MF/NOMF
From each 64kbps channels output there is two pairs. One pair is transmitting pair
and another pair is receiving pair. Two pairs then connected to corresponding leased circuit
exchange side modem. A two wire output from the modem is connected to the customer required
point using landline twisted copper pair.
So Exchange side modem has facility for 4 wire input and a 2 wire output with RJ-11 or RJ-45
connectors.
Leased-Line Modems
A Leased Line modem is a high-speed modem designed for use in a private communications channel
leased from a common carrier. Most digital lines require four wires (two pairs) for full-duplex
transmission. It may have built-in lower speeds for alternate use in dial-up lines.
A leased line is a fixed, dedicated, digital, point to point line for data transfer. The term "leased line"
is a general description of a point to point circuit from a data carrier supplier. These circuits can be
supplied at various speeds and be presented at your site with various interfaces. A leased line is not
connected to a telephone exchange and does not provide DC power, dial tone, busy tone or ring
signal.
Transmission speeds of leased lines vary from 64kbps up to several megabytes, but the costs
increase dramatically beyond 128kbps. For most small companies or home users, ISDN is quite
suitable, as it is capable of speeds of up to 128kbps. Unlike ISDN, there is no usage charge for a
leased line, only fixed annual costs, which is at a higher rate than ISDN. Due to usage charges, it is
generally recommended that if you are using the ISDN line for more than four hours a day (total on-
line time), then it may be more cost effective to move to a fixed circuit.
An added complication to working out the cost effectiveness of a leased line, is that the majority of
circuit suppliers work out the annual cost, based on the distance between the two sites to be
connected.
Leased Line Modem
Leased line modems are also called Baseband modems or short-range modems. A leased
line modem is a digital modem that may be used to inter-connect computers, terminals, controllers
and similar digital equipment over distances of up to 16 kms (10 miles) for LAN interconnection,
campus networking, or high-speed leased line internet links, over a single, unshielded twisted
copper pair (two wires).
These devices overcome distance limitations and noise problems by using special
modulation and line equalization techniques and allow error-free communication over longer
distances, at much higher data rates than conventional analog dial-up modems. Leased line modems
are a cost effective and efficient solution for dedicated data-network access and in the "last mile"
network access applications.
At Kodad Different subscribers are equipped with different types of modems due to the modems
should be purchased by the customer. In those modems there also is a provision for electronic loop
facility for testing.
2Mbps Leased Lines
2mbps leased lines are connected without MUX to the 2 Mbps E1 channels of STM-16.

55
MLLN
DRAWBACK OF TRADITIONAL LEASED LINE CIRCUITS
1. Grew from 64 kbps they have to jump over to 2 Mbps only.
2. Data Cards support only up to 64 Kbps
3. From Operator pt of view in case of Leased Line Circuit different boxes from different
vendors so difficult to manage & control.
4. No Centralized Monitoring or alarm or performance monitoring.
5. Therefore we should have a control to all this, we are able to identify before the customer
know which circuit has gone faulty The solution to this is MLLN
MLLN: Managed Leased Line Network.
For a normal leased line several modems are required at each termination of
network and also provided for only 64Kbps or 2Mbps only. Hence network is complicated and
cannot monitor centrally.
The MLLN is a managed leased line network systems which is proposed to provide
leased line connectivity with the state-of-the-art technology equipment, MLLN is designed mainly for
having effective control and monitor on the leased line so that the down time is very much
minimised and circuit efficiency is increased this achieving more customer satisfaction.
In Kodad out of 45 leased line circuit 24 circuits are provided with MLLN .In MLLN
network conventional PCM primary MUX and subscriber modems are replaced by versatile MUX and
network terminating unit(NTU) respectively.
MLLN mainly consist of digital cross connect (DXC), Versatile MUX (VMUX),
network terminating unit(NTU) and network management system (NMS). DXC’S and VMUX’S are
interconnecting via OFC links. VMUX in term connected to NTU’s via landline copper pair.
At overall system NMS is suitably placed at the central location for effective control
monitoring of leased line. NTU’s are fully managed from NMS. They can be programmable for
different data speeds ranging from 64Kbps to 2Mbps depending on customer demand.
OFC links
Landline
Main
DXC
NMS
DXC DXC DXC
VMUX VMUX VMUX VMUX VMUX VMUX
NTU NTU

Industrial Training Record BSNL Kodad

Industrial Training Record BSNL Kodad

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