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

http://en.wikipedia.org/wiki/State-owned

http://en.wikipedia.org/wiki/State-owned

http://en.wikipedia.org/wiki/Telecommunications

http://en.wikipedia.org/wiki/New_Delhi

http://en.wikipedia.org/wiki/File:BSNL_Logo.svg

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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

http://en.wikipedia.org/wiki/Internet_access

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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

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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.

http://en.wikipedia.org/wiki/Telecommunication

http://en.wikipedia.org/wiki/Sound

http://en.wikipedia.org/wiki/Human_voice

http://en.wikipedia.org/wiki/Transmitter

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.

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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.

24


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

25


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.

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• 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.

33


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.

http://en.wikipedia.org/wiki/Internet_access

http://en.wikipedia.org/wiki/Bharat_Sanchar_Nigam_Limited

http://en.wikipedia.org/wiki/India

http://en.wikipedia.org/wiki/BSNL_Broadband#cite_note-1

http://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style/Dates_and_numbers#Chronological_items

http://en.wikipedia.org/wiki/Gigabit

http://en.wikipedia.org/wiki/Protocol_(computing)

http://en.wikipedia.org/wiki/Internet_Protocol

http://en.wikipedia.org/wiki/Digital_subscriber_line

http://en.wikipedia.org/wiki/Plain_old_telephone_service

http://en.wikipedia.org/wiki/Video

http://en.wikipedia.org/wiki/Multicasting

http://en.wikipedia.org/wiki/Video-on-demand

http://en.wikipedia.org/wiki/Audio_conferencing

http://en.wikipedia.org/wiki/Video_conferencing

http://en.wikipedia.org/wiki/Video_conferencing

http://en.wikipedia.org/wiki/IP_telephony

http://en.wikipedia.org/wiki/Distance_learning

http://en.wikipedia.org/wiki/MPLS

http://en.wikipedia.org/wiki/VPN

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.

http://en.wikipedia.org/wiki/Multi_Protocol_Label_Switching

http://en.wikipedia.org/wiki/Computer_network

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

http://en.wikipedia.org/wiki/Computer

http://en.wikipedia.org/wiki/Router_(computing)


http://en.wikipedia.org/wiki/Internet

http://en.wikipedia.org/wiki/Home_router

http://en.wikipedia.org/wiki/Ethernet

http://en.wikipedia.org/wiki/Wireless_access_point

http://en.wikipedia.org/wiki/Residential_gateway


http://en.wikipedia.org/wiki/USB

http://en.wikipedia.org/wiki/USB_cable


http://en.wikipedia.org/wiki/Wireless_network

http://en.wikipedia.org/wiki/Wireless_network

http://en.wikipedia.org/wiki/Wall_wart

http://en.wikipedia.org/wiki/Telephone_exchange

http://en.wikipedia.org/wiki/DSLAM

http://en.wikipedia.org/wiki/IP_address

http://en.wikipedia.org/wiki/DHCP

http://en.wikipedia.org/wiki/Residential_gateway

http://en.wikipedia.org/wiki/ADSL2

http://en.wikipedia.org/wiki/ADSL2%2B

http://en.wikipedia.org/wiki/Routing

http://en.wikipedia.org/wiki/Network_Address_Translation

http://en.wikipedia.org/wiki/IPv4

http://en.wikipedia.org/wiki/802.11b

http://en.wikipedia.org/wiki/802.11g

http://en.wikipedia.org/wiki/802.11n


http://en.wikipedia.org/wiki/Network_switch

http://en.wikipedia.org/wiki/VPN

http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol

http://en.wikipedia.org/wiki/Dynamic_DNS

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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.

http://en.wikipedia.org/wiki/Voice_over_Internet_Protocol

http://en.wikipedia.org/wiki/Quality_of_Service

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).

http://en.wikipedia.org/wiki/Digital_subscriber_line_access_multiplexer

http://en.wikipedia.org/wiki/Internet_service_provider


http://en.wikipedia.org/wiki/Access_network

http://en.wikipedia.org/wiki/Quality_of_Service


http://en.wikipedia.org/wiki/Point-to-Point_Protocol


http://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode



http://en.wikipedia.org/wiki/PPPoE

http://en.wikipedia.org/wiki/PPPoA

http://tools.ietf.org/html/rfc1483

http://tools.ietf.org/html/rfc1490

http://en.wikipedia.org/wiki/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.

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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.

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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

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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

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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.

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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

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Features of MLLN: 1) Control and manage the leased line network.

2) Bandwidth management as the customer requirement

3) Pro-active maintenance, without waiting for customer to book a complaint.

4) Self diagnostic/software loops to check E1 connectivity to DXC,

VMUX/software loops for checking copper pair at NTU point for

immediately identifying the faulty section for trouble shooting.

5) Alternate routing in case of any route failure.

6) Generation of the periodic performance reports for self analysis.

GSM

GSM (Global System for mobile communications, originally group special mobile) is a

standard developed by the European telecommunications standards institute [EISI] to

describe protocol for second generation (2G) digital cell networks used by mobile phones.

CONCEPT OF CELLULAR SYSTEM:

The principle of cellular system is, each cellular service area is divided

into small regions called cells.

Each cell contains an antenna and is controlled by base station.Each base

station is controlled by mobile switching center (MSC) also coordinates the communication

between base stations and PSTN.

SIGNIFICATION OF FREQUENCY REUSE:

Frequency reuse is the process in which the same set of frequencies (channels) can

be allocated to more than one cell.

The frequency reuse cells are separated by sufficient distance for reducing co-channel

interference.

A cellular radio coverage area containing three clusters (group of cells).

Each cluster has seven cells in it and the cells with the same letter use the same set of

channel frequencies.The same set of frequencies used in all three clusters which essentially

increases the number of usable cellular channels available three fold. The letter A, B, C, D, E,

F and G denote the seven sets of frequencies.

The concept of frequency reuse in a cellular telephone system.

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GSM REFERENCE ARCHETECTURE AND FUNCTIONS:

The GSM system architecture consist of three major inter connected

subsystems that interact among one another.

1: Base station subsystem (BSS)

2: Network switching subsystem (NSS)

3: Operational support subsystem (OSS)

MOBILE STATION (MS):

The mobile station consists of two unit’s mobile handset with battery and

subscribes identity mobile (SIM).

The mobile station is also subsystem but it is usually considered to be part of base station

subsystem (BSS).

1: BASE STATION SUBSYSTEM (BSS):

The BSS is sometimes known as the radio system because it provides

and managers radio – frequency transmission paths between mobile station (MS) and

mobile switching Centre (MSC).

*It consist of two main parts they are,

*Base transceiver station (BTS).

*Base station controller (BSC).

FUNCTION OF BSS (BASE STATION SUBSYSTEM):

It has base station control (BSC) and one or more base stations transceivers (BTS).

*The functions of base station subsystem are:

The radio resource management like speech, data and signalling channels.

Allocation and decoction (Release) of channels for call setup and release.

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*BASE TRANSCEIVER STATION (BTS):

It consists of antennas that transmit and receive to directly

communicate with the mobiles. The BTS’S are connected to BSC.

*BTS functions and physical elements:

BTS processor

Radio transceiver

Equalizers

Channel coders

Encryption unit

Combiners

Pre-selectors

*BASE STATION CONTROLLER (BSC):

Each BSC control several BTS’s. It managers channel allocation and handoff of calls

from one BTS to another BTS. The BSC’S are connected to MSC. It provides path from MS to

MSC.

*BSC Functions and physical elements:

BSC Processor

Control of several BTS

Radio resource management(i.e. call setup, maintain and call remove)

Handoff future management and control

It provides path from MS to MSC.

2: NETWORK SWITCHING SUBSYSTEM (NSS):

It provides main control and interfacing for the whole mobile network. It

allows MSC’S to communicate with other telephone networks such as Public Switched

Telephone Network (PSTN) and integrated service digital network (ISDN).

The NSS consist of MSC, HLR, VLR and AUC.

*Mobile Switching Centre (MSC):

The MSC is heart of the entire network connecting the fixed line networks

(ISDN, PSTN etc----) to the mobiles. It manages all call- related functions and billing

information.

It is connected to HLR and VLR for subscriber identification and for routing

incoming calls.

It is also connected to AUC for authentication

Functions of MSC:

It performs the following functions.

Call setup

Supervision and release

Call routing

Billing information

Each cancellation

Integration of various registers(HLR AND VLR)

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Manage connection to BSS, other MSC and PSTN

Home Location Register (HLR):

All the subscribe data is stored in HLR. It has a permanent data base of the entire

registered subscribers.

When a user switch ON the phone, the phone registers with the network and from

there it is possible to determine which BTS it communicates with so that the incoming calls

can be routed appropriately.

Functions of Home location register:

It maintains the following mobile station user’s data on permanent basis.

Internal mobile subscriber identity (IMSI)

Service subscription information

Service restrictions

Billing and accounting information

Visitor Location Register (VLR):

An active subscriber is registered in VLR. It has temporary database of all the

active subscribers used for their call routing. The MSC asks VLR before routing incoming

calls.

Functions of VLR:

It is a temporary data storage system of mobile station user. It stores temporary

the user following information.

Features currently activated

Temporary mobile station identity.

Information of current location of mobile station.

AUTHENTICATION CENTRE (AUC):

The AUC is a protected database that contains the secret keys also

contained in the users SIM cards. It is used for authentication. Authentication is a process to

verify the subscriber SIM.

Secret data and verification algorithms are stored in the AUC. The AUC

and HLR combine to authenticate the subscribers. Subscriber authentication can be done on

every call, if required.

AUC contains a Equipment Identity Register (EIR). The entire

subscriber’s mobile handset data is stored in EIR. Each mobile equipment has a International

Mobile Equipment Identity (IMEI). This IMEI is installed in equipment and is checked by the

network during registration. EIR identifies stolen or fraudulent phones that identity the data

that does not match information contain in either the HLR or VLR.

AUC Function:

In GSM systems AUC maintains AU Keys and algorithms. It provides security

measures like encryption.

Function of Equipment Identity Registers:

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It maintains information about AU mobile station (valid

handset). So that stolen, non type approved or fraudulent mobile station can be identify as

surface can be denied.

3: OPERATIONAL SUPPORT SUBSYSTE (OSS):

It supports one or several operation and maintenance centre (OMC),

which is used to monitor and maintain the performance of each MS, BSC and MSC’S with in

a GSM system.

2G/3G BTS INTRODUCTION:- A base transceiver station (BTS) is a piece of equipment that facilitates wireless communication

between user equipment (UE) and a network. User Equipments are devices like mobile

phones (handsets), WLL phones, computers with wireless Internet connectivity. The network can be that

of any of the wireless communication technologies like GSM, CDMA, wireless local loop, Wi-Fi, WiMAX or

other wide area network(WAN) technology.

BTS is also referred to as the radio base station (RBS), node B (in 3G Networks) or, simply, the base

station (BS). For discussion of the LTE standard the abbreviation eNB for evolved node B is widely used.

Though the term BTS can be applicable to any of the wireless communication standards, it is generally

associated with mobile communication technologies like GSM and CDMA. At Kodad town there are 5 no. of BTSs are located at various places in the town. For Nalgonda

SSA the ZTE Company provides BTS services. A ZTE BTS of 2G/3G was installed in Kodad MBM premises.

The observed architecture is as follows

OFC media from Nalgonda BSC is directly given to the CC card. From FS card of Base

band Unit OFC links are connected RF cards of RF Unit. For 2G two RF cards and for 3G

another two RF cards provided. From RF cards three sectors RF cables for 2G and another

three sectors RF cables for 3G are going out and connected to the 3 - BTS antennas on the

tower.

For E1 link SA card is provided if BTS is working for 2G only one E1 (i.e.2mbps) is enough but

whenever 3G is activated high bandwidth is required. So 40 Mbps bandwidth is taken from

STM-16 ring system with fibre and connected to CC cards OFC slots. The RF light on RF cards

indicates the BTS is running and radiating RF signals from RF cards. RF cables carry the

signals from BTS to the sector type antennas.

http://en.wikipedia.org/wiki/Wireless

http://en.wikipedia.org/wiki/User_equipment

http://en.wikipedia.org/wiki/Mobile_phone

http://en.wikipedia.org/wiki/Mobile_phone

http://en.wikipedia.org/wiki/Wireless_local_loop

http://en.wikipedia.org/wiki/Computers

http://en.wikipedia.org/wiki/Wireless_Internet

http://en.wikipedia.org/wiki/GSM

http://en.wikipedia.org/wiki/CDMA

http://en.wikipedia.org/wiki/Wireless_local_loop

http://en.wikipedia.org/wiki/Wi-Fi

http://en.wikipedia.org/wiki/WiMAX

http://en.wikipedia.org/wiki/Wide_area_network

http://en.wikipedia.org/wiki/Node_B

http://en.wikipedia.org/wiki/3G

http://en.wikipedia.org/wiki/3GPP_Long_Term_Evolution

http://en.wikipedia.org/wiki/EnodeB

http://en.wikipedia.org/wiki/Wireless_communication

http://en.wikipedia.org/wiki/GSM

http://en.wikipedia.org/wiki/CDMA

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General Architecture of BTS

BTS has three levels-:

-Antenna Coupling Level (ANC)

-Transceiver Level (TRX)

-Base Station Control Function (BCF) level

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1. Antenna Coupling Level (ANC)

Stage b/w antenna & TRX Levels

A single module called ANC perform these functions for up to 4 TRXs.

For higher capacity, a combiner stage can be added.

2. TRX(Transceiver Level)

Transceiver Equipment…

Used for reception & transmission of signals.

One ARFCN is allotted to one TRX. & each ARFCN is divided in 8 time slots; hence one

TRX can provide connection to 8 subscribers at a time…

One BTS= 12 TRX=12 ARFCN=12x8= 96 users….

At a time only 96 users can make calls….

Base Station Control Function (BCF)

This station is ensured by Station Unit Module (SUMA): central unit of BTS.

Only one SUMA for one BTS….

Generating clocks for all other BTS modules.(synchronization purpose)

e.g. Abis link…..

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3G 3G is the Third Generation of Mobile Tele Communications technology.

3G phone and network should comply with the standards of ITU-2000 (International

Telecommunication Union – 2000).

3G APPLICATIONS ARE: (1) Voce telephony

(2) Mobile Internet

(3) Fixed wireless Telephony

(4) Video Calls

(5) Mobile TV

MINIMUM SPEED OF 3G IS 200Kbps.

And Maximum speed is up to several Mbps depending on network coverage and

technology adopted.

The following technologies generally branded as 3g.

(1) UMTS-SYSTEM (universal mobile telecommunication system)

(2) TD-SCDMA (time division synchronous code division multiple access)

(3) WCDMA (Wide band coded division multiple access)

(4) HSDPA and HSPA+ (high speed data pocket access)

Among the above technologies WCDMA is mostly adopted for 3G.

It was developed in 2000 but commercially available to the customers in the 2003

and launched by Hutchison telecommunications.

The 1st launch of 3G in India was done by MTNL in Mumbai.

BSNL launched 3G services in India on 11th DEC 2009.After that 3G

spectrum was allotted to all private operations in India.

Technology- Speed

GSM -9.6 Kbps

GPRS -171Kbps

WCDMA -2Mbps

HSDPA – 1 to 10 Mbps

*At Kodad BSNL exchange one 2G/3G BTS manufactured by ZTE was installed for

simultaneous radiation of 2G and 3G. Another three BTS’s are also with 3G coverage are

installed at KVB bank, Micro Wave station near SANA College and Balaji nagar.

*2G coverage is good but where as 3G coverage is less compared to 2G. 2G coverage is

up to several kilometres but where as 3G coverage is poor 0.5 to 1.5 km only from the

BTS.

*At Kodad, customers mostly used BSNL 3G SIMs for mobile data with high speed.The

data rate achived practically is 200 Kbps to 7 Mbps depending on the distance from the

3G BSNL tower.

*BSNL strictly following TRAI (Telecom Regulatory Authority of India) guide lines for

radiation strength and do not increased above the limit set by TRAI. Hence compared to

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private operators BSNL 3G coverage is less and many more towers to be constructed for

better coverage of 3G. Approximately one tower is required for a square km area.

*Hence more budgets is required and also very typical task. Hence 3G development is

very slow. And also next coming technology 4G also steps down the 3G technology.

FREQUENCY BAND:

3G frequency band is 2100 MHz

Uplink range – 1920 – 1980 MHz

Downlink range – 2110 – 2170 MHz

4G 4G- Fourth Generation of Mobile Telecommunications Technology.

A 4G systems provides ULTRA-BROADBAND MOBILE INTERNET ACCESS in addition to the normal

voice and other services of 3G. ULTRA BROADBAND means minimum speed of 100Mbps in moving

position and may reach the speeds up to 1Gbps speed, in standstill position.

The 4G standards are stated by ITU-R (International Telecommunications union radio

communications sector) and named as IMT-advanced (International Telecommunications

advanced).The standards of 4G set the speeds as 300 Mbps for high mobility (such as trains, cars)

1 Gbps for low mobility (by walk or stationary).

The latest technologies are like: 1. Mobile Wimax version 2

2. LTE advanced (Long Term Evolution advanced) are supports 4G and they

can achieve those speeds.

The 4G does not supports traditional circuits switched telephony. But it supports all IP based

communication.

LTE advanced technology provides the speeds up to

1.1Gbps in peak download

2.500Mbps in peak up load

Wimax version 2(IEEE 802.16m) provides

1.128Mbps in peak down load

2. 56Mbps in peak upload

* Bharthi Airtel launched India’s 1st 4G services using TD-LTE technology is KOLKATA on April

10th of 2012. Then extends to Bangalore, Pune and Chandigarh in July 2014 Airtel 4G also entered in

AP, Assam, Bihar and Orissa.

Reliance also provides 4G in Delhi, Mumbai and Kolkata. BSNL is going to be

implementing 4G shortly all over the India.

4G also called as MAGIC: M- Mobile multimedia

A- Any time any where

G- Global mobility supports

I- Integrated wireless solution

C- Customised personal services

4G also provides high security and high quality of services (QOS) along with high speed services.

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Draw backs of 4G are: 1. High battery usage

2. Hard to implement

3. Need complicated hardware & expensive.

CODE DIVISION MULTIPLE ACCESS (CDMA) Code Division Multiple Access (CDMA) consistently provides better capacity for voice and data

communications that other commercial mobile technologies, allowing more subscribers to connect

at any given time, and it is the common platform on which 3G technologies are built.

CDMA is a spread spectrum technology, allowing many users to occupy the same time and frequency

allocations in a given band/space. As it name implies, CDMA assigns unique codes to each

communication to differentiate it from others in the same spectrum resources, CDMA enables many

more people to share the airwaves at the same time than do alternative technologies.

ADVANTAGES OF CDMA:

Increased cellular communications security.

Simultaneous conversations

Increased efficiency, meaning that the carrier can serve more subscribers.

Smaller phones

Low power requirements and little cell-to-cell coordination needed by operators.

Extended reach-beneficial to rural users situated far from cells. DISADVANTAGES OF CDMA:

Due to its proprietary nature, all of CDMA’s flaws are not known to the engineering community.

CDMA is relatively new, and the network is not as mature as GSM.

CDMA cannot offer international roaming, a large GSM advantage. DIFFERENCE BETWEEN CDMA AND GSM:

The GSM stands for global system for mobile communication and CDMA for code division multiple accesses.

GSM is a form of multiplexing, which divides the available bandwidth among the different channels. Most of the times the multiplexing used are either TDM (Time Division Multiplexing) or FDM (Frequency Division Multiplexing). On the other hand CDMA is a type of multiple access scheme (which means allotting the given bandwidth to multiple users) and makes use of spread spectrum technique which is essentially increasing the size of spectrum.

In CDMA each user is provided a unique code and all the conversations between 2 users are coded. This provides a greater level of security to CDMA users than the GSM ones.

At Kodad BSNL installed a CDMA BTS at microwave station for providing WLL phones, Prepaid and

post paid CDMA mobile SIM card services and WLL FWTs (Fixed wireless Terminal) around Kodad.

NIC (Network Interface Card) data cards, EVDO (Enhanced Voice Data Optimized) data cards are also

provided for Internet connection by using CDMA technology.

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Optical Fiber Cable

• An optical fiber is a hair thin cylindrical fiber of glass or any transparent dielectric medium.

• The fiber which are used for optical communication are wave guides made of transparent

dielectrics.

• Its function is to guide visible and infrared light over long distances.

• Structure of optical fiber

• Core – central tube of very thin size made up of optically transparent dielectric medium and

carries the light form transmitter to receiver. The core diameter can vary from about 5um to

100 um.

• Cladding – outer optical material surrounding the core having reflecting index lower than

core. It helps to keep the light within the core throughout the phenomena of total internal

reflection.

• Buffer Coating – plastic coating that protects

the fiber made of silicon rubber. The typical diameter of fiber after coating is 250-300 um.

• Working principle

Total Internal Reflection

• When a ray of light travels from a denser to a rarer medium such that the angle of incidence

is greater than the critical angle, the ray reflects back into the same medium this

phenomena is called total internal reflection.

• In the optical fiber the rays undergo repeated total number of reflections until it emerges

out of the other end of the fiber, even if the fiber is bent.

• The arrow and the bent pencil

Total internal reflection in optical fiber

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• Classification of optical fiber

• Optical fiber is classified into two categories based on :-

1) The number of modes, and

2) The refractive index

On the basis of number of modes:-

on the basis of number of modes of propagation the optical fiber are classified into two types:

(i) Single mode fiber (SMF) and

(ii) Multi-mode fiber (MMF)

• Single-mode fibers – in single mode fiber only one mode can propagate through the fiber.

This type of fiber has small core diameter(5um) and high cladding diameter(70um) and the

difference between the refractive index of core and cladding is very small. There is no

dispersion i.e. no degradation of signal during travelling through the fiber.

• The light is passed through the single mode fiber through laser diode.

• Multi-mode fiber :-

• Multi mode fiber allows a large number of modes for the light ray travelling through it.

• The core diameter is (40um) and that of cladding is(70um)

• The relative refractive index difference is also larger than single mode fiber.

• There is signal degradation due to multimode dispersion.

• They are not suitable for long distance communication due to large dispersion and

attenuation of the signal.

• On the basis of Refractive index

• There are two types of optical fiber:-

• (i) Step-index optical fiber

• (ii) Graded-index optical fiber

• Step

• Step index fiber

• The refractive index of core is constant

• The refractive index of cladding is also constant

• The light rays propagate through it in the form of meridiognal rays which cross the fiber axis

during every reflection at the core cladding boundary.

• Graded Index fiber

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• In this type of fiber core has a non uniform refractive index that gradually decrease from the

centre towards the core cladding interface.

• The cladding has a uniform refractive index.

• The light rays propagate through it in the form of skew rays or helical rays. They do not cross

the fiber axis at any time.

• How Optical Fiber’s are made??

• Three Steps are Involved in the manufacturing of the optical fiber which are given below:-

-Making a Preform Glass Cylinder

-Drawing the Fiber’s from the preform

-Testing the Fibre

• Optical Fiber Communication System

• Information source- it provides an electrical signal to a transmitter comprising an electrical

stage.

• Electrical transmitter- It drives an optical source to give an modulation of the light wave

carrier.

• Optical source- It provides the electrical-optical conversion .It may be a semiconductor laser

or an LED.

• Optical cable: It serves as transmission medium.

• Optical detector: It is responsible for optical to electrical conversion of data and hence

responsible for demodulation of the optical carrier. It may be a photodiodes,

phototransistor, and photoconductors.

Information source

Electrical source

Optical source

Optical fiber cable

Optical detector

Electrical receive

Destination

69


• Electrical receiver: It is used for electrical interfacing at the receiver end of the optical link

and to perform the signal processing electrically.

• Destination: It is the final point at which we receive the information in the form of electrical

signal.

•

Attenuation

• Attenuation is the loss of the optical power.

• Attenuation in optical fiber take place due to elements like coupler, splices, connector and

fiber itself.

• A fiber lower attenuation will allow more power to reach a receiver than with a higher

attenuation.

• Attenuation may be categorised as –

(i) Intrinsic

(ii) Extrinsic

• Factor causing attenuation in Fiber

• Fig. shows the factor affecting the attenuation in fiber-

• Variation of specific attenuation with wavelength

Attenuation & Wavelength

• Advantage of optical fiber communication

1) The life of fiber is longer than copper wire

2) Handling and installation costs of optical fiber is very nominal

Attenuation

Intrinsic

Absorption Scattering

Extrinsic

Macrobending

Microbending

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3) It is unaffected with electromagnetic interference

4) Attenuation in optical fiber is lower than coaxial cable or twisted pair.

5) There is no necessity of additional equipment for protecting against grounding and voltage

problems.

6) As it does not radiates energy any antenna or detector cannot detects it hence provides

signal security

• Disadvantage

1) Highly skilled staff would be required for maintenance

2) Only point to point working is possible on optical fiber

3) Precise and costly instruments would be required

4) Costly if underutilized.

5) Accept uni polar codes only.

6) Jointing of fiber and splicing is also time consuming.

• Applications

• In telecommunication field

• In space applications

• Broadband applications

• Computer applications industrial applications

• Mining applications

• In medical applications

• In military applications etc.

Basic fibre optic communication system with block diagram:

The block diagram of fibre optic communication system consists of mainly

1. Optical transmitter.

2. Fibre optic cable.

3. Optical receiver.

1. Optical transmitter:

It’s main function is to transmit the information signals like voice, video or

computer data in the form of light signals. The information at input is converted into digital

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signals by using A/D converter. If the input signals are computer signals they are directly

connected to light source. It consists of A/D converter and light source.

A/D converter:

The information signals like voice and video signals are analog in natures

that are converted into digital signals by using A/D converter. These digital (electrical) are

fed to light source. If the input signals are coming from the computer i.e. digital signal they

are directly connected to light source.

Light Source:

The output of the A/D converter is an electrical signal is given to light

source this light source converts electrical signal into light signal.

The light source turn ON-OFF, depends on digital pulse thus its flashing is

proportional to digital input.

EX: LED, LASER etc..

2: Fibre optical cable:

When the light pulses are coming from the optical transmitter fed to one

end of fibre optic cable, they are passed on to the other end of the fibre optic cable.

3: Optical Receiver:

At the receiving end the light signals are connected into electrical signals.

The optical receiver consists of light detector and D/A converter.

Light Detector:

A light signal from the fibre optic cable at the receiving end is given to

light detector, the light detector converts light signal into electrical signal.

EX: PIN diode and Avalanche photo diode (APD).

D/A Converter:

The output of light detector is given to D/A converter which converts

digital data into analog signals. If the digital signal for computer can be directly taken from

the output of the light detector.

FDF FDF means Fibre Distribution Frame.

FDF includes metallic casing adaptor plat, splice tray and other necessary materials for the

termination of optical fibre cables.

FDF is a metallic frame which supports fibre connectors which are fixed and used from cross

connecting outside and exchange side fibres. The pigtails from the outside OFC cable are

terminated on left side and the exchange side OFC patch cards are terminated on the right

side of FDF to the corresponding outgoing fibre. The OFC connectors which are fixed to

metal frame are three types

1. 0 dB means no loss in connection.

2. 5dB means 5dB loss between outside and exchange side fibre.

3. 10dB means 10dB loss between outside and exchange side fibre.

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These are used reduce the transmitter to receive power between short distance

communications. If long distance communications 0dB connectors are used.

DDF The Digital Distributing Frame (DDF) is a 75 ohms frame system that serves as an equal level

cross connects point for signals conforming to the following signal formats:

2.048mbps

8.448mbps

34.368mbps

139.264mbps

155.52mbps

The modules allow test access to all equipment terminated at the frame and provide flexible cross

connects between network elements (NE’s). The DDF system consists of individual DDF modules

mounted in a panel.

In kodad for STM-16 there are 3 TM’s means 63 no of 2Mbps E1 channels per each TM are physically

terminated to the DDF on right side with permanent wiring. The trunks from MBM switch, E1s from

MLLN system, E1s from leased lines, E1s from rural cell BTSs and other equipments are terminated

to the left side Of the DDF. For all these E1s two pair twisted copper pairs are used. For the

termination purpose a unique is known as WRAPPING TOOL is used. On the front loop test with loop

card for conforming the channel is working or not on left side and the corresponding signal is

arriving or not on right side of the DDF. The left side to right side is jointing with links called as “U-

links”.

CPE (customer Premises Equipment) for OFC systems

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CPE means It is an interface system at the fiber end which facilitates several E1s, Ehternet

ports, and Optical fibre ports with STM-1 configuration. Generally several E1s, Ethernet ports and

fiber ports are given as input and one fiber port taken as output or as vice versa.

E1’s

Ethernet OFC –STM1

Optical port

Overview: Ultra-compact Customer Premise Equipment with STM-1, E1 and 10/100 Mbps Ethernet

interfaces in a fixed configuration. It combines innovative optical networking software, with the

intelligence of SDH/SONET, to deliver an efficient solution to today's service providers.

Ideal Environment: It is designed for the access part of optical network with low to medium traffic

volume. It can be used in multiple access applications – transport of E1 & Ethernet from 2G/2.5G/3G

wireless backhaul, DSLAM aggregation from remote locations & enterprise connectivity.

Compact Node: It is a compact 1U STM-1 node with E1 & Ethernet that serves a wide scope of

access needs. It is a cost effective, low-power and easy to manage equipment with plug & play

benefits.

Various Topologies: It fits into liner, ring, bus and mesh topologies. It can be configured as a

Terminal Multiplexer (TMUX) or an Add-Drop Multiplexer (ADM). Thus it caters to all possible access

network scenarios.

At Kodad generally we find Tejas and ITI CPEs having

8 ports for E1s

2STM-1 ports,

2 optical ports and

2 Ethernet ports.

STM-16 STM means Synchronous Transport Module

STM-16 is an OFC system which is used at Kodad main exchange for the purpose of OFC

network communication from Kodad to Nalgonda & Kodad to Huzunagar.

Generally OFC systems use two types of hierarchies:

1) PDH- Physiological digital hierarchy

2) SDH-Synchronous digital hierarchy.

STM uses the SDH & following STMs are developed according to ITU standards.

STM-0 is configured for 21 E1 channels with a bit of 51.84 mbps

STM-1 “ “ “ 63 E1 “ “ “ “ 155.52mbps

STM-4 “ “ “ 251E1 “ “ “ “ 622.08 mbps

STM-16 “ “ “ 1008 E1 “ “ “ 2488.32 mbps

STM-64 “ “ “ 4032E1 “ “ “ “ 9953.38 mbps

[E1 means a 2 mbps electrical digital signal channel having one Trans pair & one receive

pair of copper conductor].

TM means transport module having 63 no of E1’s and TM is also called as E4.

OFC

CPE

OFC

CPE

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In Kodad main exchange all the trunks of main exchange, all BB channels, all leased

lines channels, all cell BTS s channels and all other communicating channels which are to be

connected to Nalgonda and all the rural exchanges of Huzurnagar are terminated to the

TM’s of STM-16 out of 16 TMs 3TMs physically terminated using DDF, another 3 fiber

outputs for 3G Cell BTS’s each of 40Mbps and one fiber output for Broadband with 455

Mbps bandwidth are configured.

For OFC transmission BSNL uses ring structure of connectivity using STM16

systems located at various exchanges Kodad, Huzurnagar, Miryalaguda, Nalgonda, Nakrekal

and Suryapet are formed a ring structure using STM16 systems in each exchange. So

redundancy of network is possible. Whenever route break occurred towards Huzurnagar

side then the system will work with another direction towards Suryapet. So STM-16

provides connectivity of large no. of E1s i.e. 1008 no. of E1s with ring structure for route

redundancy

STM – 16

Ring system

OFC Network

Kodad to NLG

STM-4 STM -4 was installed in kodad exchange with bandwidth is 622.08mbps.

As the requirement of band width and no of E1’s are increasing for newer equipments the

STM – 16 was installed and the STM-4 was kept idle in KODAD MBM.

Digital microwave radio systems

Digital microwave radio relay is a technology for transmitting (transmit and receive) data/signals between two points in telecommunication network that can be distanced over 80 km. Standard digital radio station is built out of three main components:

Digital modem as an interface with terminal equipment, Radio unit as a converter of user data/signals into the signals adjusted for transmitting

over the air, and Antenna system as an element which transmits and receives radio waves.

Two fixed microwave radio stations are required for one microwave radio relay link. Digital microwave radio relay systems offer flexibility, simplicity and deployment speed of

KDD

HZN

MYG

NLG

NKR

SRT

75


telecommunication networks. Applications:

Backbone for mobile operators, BWA operators and similar applications (TETRA networks),

Last mile access, Private networks, Disaster recovery systems, Public safety, Government and defence, Health and education.

All Outdoor Type DMW equipment

• All the units are outdoor. • Installation is easy. • The equipment room can be saved.

Split type Microwave Equipment

The RF unit is an outdoor unit (ODU). The IF, signal processing, and MUX/DEMUX units are integrated in the indoor unit (IDU). The ODU and IDU are connected through an IF cable.

The ODU can either be directly mounted onto the antenna or connected to the antenna through a short soft waveguide.

Although the capacity is smaller than the trunk, due to the easy installation and maintenance, fast network construction, it’s the most widely used microwave equipment.

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Unit Functions

Antenna: Focuses the RF signals transmitted by ODUs and increases the signal gain.

ODU: RF processing, conversion of IF/RF signals. IF cable: Transmitting of IF signal, management signal and power supply of ODU. IDU: Performs access, dispatch, multiplex/demultiplex, and

modulation/demodulation for services.

At Kodad exchange we find the DMW systems are equipped as follows

1) Three Split model DMWs are installed for communicating E1s for 1) Cell BTS – KVB at Kodad 2) Cell BTS—Balaji nagar 3) Cell BTS—Akupamula

2) Two fully Outdoor DMWs are installed for communicating 10 Mbps Broadband Internet Connections for

1) Anurag Engineering College 2) GATE Engineering College

General problems and maintanance 1) The antenna positions may disturb. 2) The IF cable or POE cables may damaged 3) The RF convertors may damage.

WIMAX

WiMAX acronym meaning is “Worldwide Interoperability for Microwave Access”.

WiMAX is a wireless communications standard designed to provide 30 to 40 Mbps data

rates,[1]

with the 2011 update providing up to 1 Gbit/s[1]

for fixed stations.

WiMAX is "a standards-based technology enabling the delivery of last mile wireless

broadband access as an alternative to landline cable and DSL".

It is an IP based Wireless Broadband Access Technology utilizing IEEE 802.16e-2005

standard as the air interface.

The standards are similar to the Wi-Fi (IEEE 802.11). With Wi-Fi we can achieve wireless

connectivity with in very short distance in several meters where as with WiMAX coverage is spread

over several kilometres.

http://en.wikipedia.org/wiki/Wireless

http://en.wikipedia.org/wiki/WiMAX#cite_note-Carl_Weinschenk-1

http://en.wikipedia.org/wiki/WiMAX#cite_note-Carl_Weinschenk-1

http://en.wikipedia.org/wiki/Last_mile

http://en.wikipedia.org/wiki/Wireless_broadband

http://en.wikipedia.org/wiki/Wireless_broadband

http://en.wikipedia.org/wiki/Cable_modem


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Instead of Landline BSNL uses this technology for providing broadband with the speeds up

to 2Mbps in rural areas where landline is not available. In Kodad BSNL exchange there is a WiMAX

BTS installed and it can capable of 15 km radius coverage with maximum speed of 2 Mbps to each

subscriber. The WiMAX BTS is connected to the BBRAS with OFC backhaul network of BSNL.

We can get the Internet access everywhere in home and in the office. No Wire Required:

No Wire, No Telephone connection required. Wimax setup and activation are quick and fast. The

WiMAX connections can easily and immediately provided as their activation and configuration of

WiMAX modems are very easy compared to the ADSL Modems. The faults occurring are very less

due to wireless communication and more the customer satisfaction.

BSNL provided WiMAX connections with three types of modems i.e. USB WiMAX Dongle,

Indoor WiMAX Modem and Outdoor WiMAX Modem. The USB and Indoor Modems are accessible

only with in short distance i.e. 1 km but whereas Out Door Modem can serve up to 15 km.

BSNL KODAD provided nearly 300 WiMAX connections around the Kodada town where

landline connection is not feasible. But BSNL handed over its Spectrum back to Central

Government and closed Wimax services all over the India except in special category states on 8th

June of 2014.

The next generation standards of WiMAX (IEEE802.16m) are developed in 2011 and are

currently being used in 4G technology along with the LTE (Long Term Evolution) technology to

achieve the mobile broadband speeds up to 1 Gbps.

Wi-max modem The modems of wi-max technology are three types.

1. USB dongle.

2. Indoor modem.

3. Outdoor modem.

1. USB dongle:-

It can access internet very nearer to the wi-max BTS.

2. Indoor modem

It can access internet up to 1 km only. It has two small antennas. An Ethernet cable

can be directly connected from modem to PC. No other equipment is needed.

3. Outdoor modem:-

It can access internet up to the 15 km. The modem was installed

permanently on the roof top of the customer building and the direction of the outdoor

modem should be in the line of sight to the wimax BTS situated at Exchange premises. If

there is no line of sight or if any obstruction, the internet can’t be accessed. Near

subscribers PC one POE power adapter is fixed. From POE adapter one Ethernet cable is

connected to outdoor modem which carries Power Over Ethernet and the corresponding

signal. For this purpose cat-5 cable with straight connection is used. And one Ethernet cable

is connected from POE adaptor’s LAN port to the PC. Main advantage of wimax connection

over normal landline broadband connection are as follows.

1) No. Of wire connections at subs primises are less.

2) Due to air media fault rate is very less.

3) Modem configuration is very easy.

4) No. Of errors are very less.

5) Connection can be provided very easily and quickly.

6) Cost also is less compared to BB installation.

The disadvantages are as follows

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1) Speeds cannot be provided above 2Mbps.

2) Signal coverage is poor for indoor modems and USB dongles.

3) Line of sight is compulsory for outdoor modems.

Outdoor wimax modem.

POE cable straight

And 8 wire

Ethernet cable

POE adaptor

FTTH FTTH (fiber-to-the-home): Fiber reaches the boundary of the living space, such as a box on the

outside wall of a home. Passive optical networks and point-to-point Ethernet are architectures that

deliver triple-play services over FTTH networks directly from an operator's central office.

Fibre to the Home (FTTH) is a unique technology being deployed by BSNL for the first time in India. The fibre connectivity having unlimited bandwidth and state of the art technology provides fix access platform to deliver the high speed broadband from 256 Kbps to 100 Mbps, IPTV having different type of contents like HDTV and future coming 3D TV and range of voice telephony services. It provides a comprehensive solution for the IP leased line, internet, Closed User Group (CUG), MPLS-VPN, VoIP, video conferencing, video calls etc whatever the services available on the internet platform, bandwidth on demand can be delivered by this connectivity to the without changing the access fibre and home device. Customer will get a CPE called Home Optical Network Termination (HONT) consist of 4X100 Mpbs Ethernet ports and 2 normal telephone ports. Each 100 Mbps ports will provide broadband, IPTVs, IP Video call and leased line etc as required by the customers. Customer will get power back unit having full load backup of four hours and normal backup of three days. This power backup will be AC input and connecting to the HONT on 12V DC. Connectivity via FTTH: BSNL will extend fibre from its nearest Central Office (CO) location directly or through franchisee and install HONT and battery backup at the customers identified locations. The services such as Voice, Broadband, IPTV etc. will be enabled as per the customer”s request plans for the same.

PC

LAN pwr

POE

power

http://en.wikipedia.org/wiki/Passive_optical_network

http://en.wikipedia.org/wiki/Point-to-point_protocol_over_Ethernet

http://en.wikipedia.org/wiki/Triple_play_(telecommunications)

http://en.wikipedia.org/wiki/Telephone_exchange

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The services over FTTH: Basic internet Access Service controlled and uncontrolled from 256Kbps to 1000Mbps.

TV over IP Service (MPEG2).

Video on Demand (VoD)(MPEG4)

Audio on Demand Service

Bandwidth on Demand (User and or service configurable)

Remote Education

Point to Point and Point to Multi Point Video Conferencing, virtual classroom

Voice and Video Telephony over IP: Connection under control of centrally located soft switches

Interactive Gaming

VPN on broadband

Dial up VPN Service

Virtual Private LAN Service (VPLS)

BSNL INTRANET 4.1 INTRANET:

Smaller private version of Internet. It uses Internet protocols to create enterprise-wide network which may consists of interconnected LANs.

It may or may not include connection to Internet.

Intranet is an internal information system based on Internet technology and web protocols for implementation within a corporate organization.

This implementation is performed in such a way as to transparently deliver the immense informational resources of an organization to each individual’s desktop with minimal cost, time and effort.

The Intranet defines your organization and displays it for everyone to see. 4.2 FEATURES OF INTRANET: 1. It is scalable. 2. It is Interchangeable.

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3. It is platform independent 4. It is Hardware independent. 5. It is vendor independent.

4.3 WHY INTRANET FOR AN ORGANIZATION:

Quick access to voice, video, data and other resources needed by users.

Variety of valuable Intranet applications improves communication and productivity across all areas of an enterprise.

A 21st Century Telephone.

An ISO Tool.

A Target Marketing Tool.

A Decision Making Tool.

A Complete Communication Tool.

FIG 4.1 INTRANET NETWORK (REF- 5)

4.4 APPLICATIONS OF INTRANET:

Publishing Corporate documents.

Access into searchable directories.

Excellent Mailing Facilities.

Proper Sharing of Information.

Developing Groupware Applications. 4.5 TECHNICAL OVERVIEW OF THE INTRANET TECHNOLOGY Intranet runs on open TCP/IP network, enable companies to employ the same type of servers and browser used for World Wide Web for internal applications distributed over the corporate LAN. A typical Intranet implementation involves a high end machine called a server which can be accessed by individual PCs commonly referred to as clients, through the network. The Intranet site setup can be quite inexpensive, especially if your users are already connected by LAN.

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4.6 INTRANET APPLICATIONS IN A CIRCLE: Every circle must have an intranet server which should have the following:

All posting/transfer/relieving orders issued within circle to be hosted on the intranet.

All letters circulars/letters issued from different sections of the circle office to be hosted on the server for immediate access by SSAs. Each section in circle office Administration, Operations, Marketing, Finance, Planning, Computers etc can have web pages hosted on the server.

A database can be maintained for MIS reports and all other reports to be sent periodically by SSAs to circle office. The database can have front end forms designed in ASP or PHP for the SSAs to input the data. Separate programs can be developed to consolidate the data fed by SSAs.

All data prepared and /or distributed during SSA heads meetings can be hosted on the Intranet.

The implementation of the above will reduce the usage of paper and also reduce the usage of FAX.

Electrical Systems in BSNL Exchange

Electricity is the most important element required to any industry or commercial organisation. For a

BSNL Exchange it is prime need to operate any equipment. The electricity supply is taken from the

electricity distribution company (TSSPDCL – Telangana State Southern Power Distribution Company

Limited) for contracted load of 70 kVA MD (Maximum Demand) with a voltage of 11000 V.

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SUB STATION

A substation is a part of an electrical generation, transmission, and distribution system.

Substations transform voltage from high to low, or the reverse, or perform any of several other

important functions. Between the generating station and consumer, electric power may flow

through several substations at different voltage levels.

Substations may be owned and operated by an electrical utility, or may be owned by a large

industrial or commercial customer. Here KODAD BSNL owned a 11 kV Sub-station. Kodad MBM exchange has taken electricity supply from TSSPDCL with a contracted load of

70KVA MD .So electricity company has given supply with HT voltage i.e. 11KV to the substation

yard of exchange then a energy meter was installed before Kodad MBM premises of

substation by the electricity company.

For incoming 11KV supply there was equipped a 11KV vertical AB(Air break) switch and

a H.G(horn gap) fuse set. Then by UG 11KV cable passed through a 11KV/110V, 5A CT/PT set. A tri

vector meter is equipped in meter panel with components taking from CT/PT set. Up to the

tri vector meter the responsibility is taken by TSSPDCL people. Every month they taken readings

and billed for current charges accordingly. From the CT/PT set the 11KV supply came to the

substation yard and to 11KV bus and from 11KV bus supply is given to two power

transformers of 11KV/415V 3ᶲ 250KVA each. The output of the transformer 415V 3ᶲ AC is

come out from the substation and connected to LT panels room. We also observed the earth

points for neutral earth, transformers body earth, iron structure earth and AB switch handles earth.

The earth resistance of this substation is being maintained at 0.5 ohm.

Electrical energy is available in two forms:

1) AC (alternating current)

2) DC (direct current)

AC electrical energy can be generated from water and coal at hydro and thermal

power stations . Then this electrical energy is to be transmitted at considerable

distances for use in cities, towns and villages.

The transmission of electrical energy at high voltages is economical, Some means are

required for stepping up the at generating stations and stepping down the same at

the places where it is to be used.

Electrical machine used for this purpose is known as transformer.

TRANSFORMER: Transformer is a static device which transfers the electrical power from one circuit to another

circuit without change in its frequency. It works on the principle of “Electro-magnetic induction”.

It is mainly used to change the voltage level of a circuit.

A varying current in the transformer's primary winding creates a varying magnetic flux in the core

and a varying magnetic field impinging on the secondary winding. This varying magnetic field at the

secondary induces a varying electromotive force (emf) or voltage in the secondary winding. The

primary and secondary windings are wrapped around a core of infinitely high magnetic

permeability[e] so that all of the magnetic flux passes through both the primary and secondary

http://en.wikipedia.org/wiki/Electricity_generation

http://en.wikipedia.org/wiki/Electric_power_transmission

http://en.wikipedia.org/wiki/Electric_power_distribution

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Transformer#cite_note-11

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windings. With voltage source connected to the primary winding and load impedance connected to

the secondary winding, the transformer currents flow in the indicated directions

Ideal transformer equations (eq.)

By Faraday's law of induction

. . . (1)[a]

. . . (2)

Combining ratio of (1) & (2)

Turns ratio . . . (3) where for step-down transformers, a > 1

for step-up transformers, a < 1

By law of Conservation of Energy, apparent,real and reactive power are each conserved in

the input and output

. . . (4)

Combining (3) & (4) with this endnote[b] yields the ideal transformer identity

. (5)

According to Faraday's law of induction, since the same magnetic flux passes through both the

primary and secondary windings in an ideal transformer,[7] a voltage is induced in each winding,

according to eq. (1) in the secondary winding case, according to eq. (2) in the primary winding

case.[8] The primary emf is sometimes termed counter emf.[9][10][f] This is in accordance with Lenz's

law, which states that induction of emf always opposes development of any such change in magnetic

field.

http://en.wikipedia.org/wiki/Voltage_source

http://en.wikipedia.org/wiki/Electrical_impedance


http://en.wikipedia.org/wiki/Conservation_of_Energy

http://en.wikipedia.org/wiki/Apparent_power

http://en.wikipedia.org/wiki/Real_power

http://en.wikipedia.org/wiki/Reactive_power


http://en.wikipedia.org/wiki/Identity_function

http://en.wikipedia.org/wiki/Transformer#cite_note-Hameyer_.2A2001a-12

http://en.wikipedia.org/wiki/Transformer#cite_note-Heathcote_.281998.29-13

http://en.wikipedia.org/wiki/Counter-electromotive_force

http://en.wikipedia.org/wiki/Transformer#cite_note-Rajut_.282002.29-14

http://en.wikipedia.org/wiki/Transformer#cite_note-Rajut_.282002.29-14


http://en.wikipedia.org/wiki/Lenz%27s_law

http://en.wikipedia.org/wiki/Lenz%27s_law

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The transformer winding voltage ratio is thus shown to be directly proportion to the winding turns

ratio according to eq. (3).[11][12][g][h]

According to the law of Conservation of Energy, any load impedance connected to the ideal

transformer's secondary winding results in conservation of apparent, real and reactive power

consistent with eq. (4).

The ideal transformer identity shown in eq. (5) is a reasonable approximation for the typical

commercial transformer, with voltage ratio and winding turns ratio both being inversely

proportional to the corresponding current ratio.

At Kodad MBM Exchange substation, two power transformers were installed with each

name plate details are

Capacity: 250 kVA,

No. Of Phases: 3 phase,

Voltage Rating: 11000/415 V,

Type of Connection: Delta/ Star connected,

Type of cooling: ONAN - Oil Natural and Air Natural cooling,

MAINTANANCE:

Generally the following preventive maintenance is carrying regularly for proper working of

transformer

Silica gel replacement: Silica gel material which is added in breather hole to prevent

moisture entrance in to conservator tank. This material absorbs moisture in the air which is

getting into tank and turns it’s colour from blue to pink. The pink colour indicates it has no

capacity to absorb moisture. Hence the silica gel has to be replaced periodically.

Oil filtering: The transformer oil serving two purposes. One is Insulation between windings

and tank and another one is cooling of windings. Whenever moisture absorbed by the oil the

insulation characteristics are destroyed. Hence the oil has to filtered periodically

Cleaning of Insulators: The dust accumulated on the insulators may act as conductor and

hence the cleaning has to carried out regularly.

Earthing resistance: The earth resistance has to maintain at 0.5 Ω. If not the neutral point

may shift, the operators may get shocked, The transformer may damaged due to lightning or

any short circuit faults.

CAPACITOR BANK A capacitor bank is a grouping of several identical capacitors interconnected in parallel or in

series with one another. These groups of capacitors are typically used to correct or counteract

undesirable characteristics, such as power factor lag in alternating current (AC) electrical power

supplies

POWER FACTOR IMPROVEMENT:

The heating and lighting loads supplied from 3-phase supply have power factor ,ranging

from 0.95 to unity .But motor loads have usually low lagging power factor, ranging from

0.5to0.9 single-phase motors may have as low a power factor as0.4 and electric welding units

have even lower power factor of 0.2or0.3.

kW

kVA kVAr

http://en.wikipedia.org/wiki/Transformer#cite_note-Winders_.282002.29-17

http://en.wikipedia.org/wiki/Transformer#cite_note-Winders_.282002.29-17



http://en.wikipedia.org/wiki/Conservation_of_Energy

http://en.wikipedia.org/wiki/Identity_function

http://www.wisegeek.com/what-is-a-capacitor.htm

http://www.wisegeek.com/what-is-power-factor.htm

http://www.wisegeek.com/what-are-the-most-common-applications-for-ac-current.htm

http://www.wisegeek.org/what-are-power-supplies.htm

http://www.wisegeek.org/what-are-power-supplies.htm

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The power factor is given by cosφ =KW/KVA or KVA = KW/COSφ

In the case of single phase supply, KVA=VI/1000 or I=1000KVA/V therefore I ԃ KVA

In the case of 3-phase supply KVA=1.71VL IL/1000 OR IL=1000KVA/1.71*VL

Therefore IL ԃ KVA.

In each case, the KVA is directly proportional to current. The chief disadvantage of a low p.f

is that the current required for a given actual power, is very high. This fact leads to the

following undesirable results like high copper losses (I square R) which leads low system efficiency

Leading kVAr Leading kVAr

kW

Lagging kVAr

kVA Couter act by leading kVAr

Hence the capacitors are used to counter act the lagging power factor. Whenever the capacitors

connected in parallel to the power supply then the corresponding leading reactive power will nullify

the same value of lagging reactive power. Hence the angle of lagging is decreased and PF will

improve or come nearer to unity.

At Kodad MBM a capacitor bank was installed in parallel to the LT bus bars in the power control

room. There is a rough estimation for the kVAr capacity. 1/3rd value of kVAr has to install in the total

value of kVA load installed. Hence in Kodad exchange for a 70 kVA Maximum Demand (MD), there is

runnig continuously a total of 25kVAr capacitors in parallel. For that purpose two 10 kVAr and one 5

kVAr capacitors were switched ON. In the capacitor panel there is also installed an “Auto PF

Controller” which will switch ON/OFF the individual capacitors up to the PF is unity and displayed the

PF value.

The capacitors bring the P.F. from 0.8 to unity value. If any circumstances the monthly average

power factor which is recorded by tri-vector meter is decreased below 0.95 the electricity company

will charged penalty and also the billing is being done for consumed kVAh, the kVAh recorded is

more for low power factor and hence more power bill has to pay.

Engine –Alternator set Whenever power failed a long time the batteries will continue to discharge and it is undesirable to

deep discharge the batteries. For this purpose two Engine –Alternator sets are installed using as

power back-up in the times of power failures. Two Diesel Engines are of 218 HP (make: Intac) and

128kW (make: Greaves) are equipped at Kodad Exchange and are using as prime movers to the

alternators.

Diesel Engine The diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition and burn the fuel that has been injected into the combustion chamber. The diesel engine has the highest thermal efficiency. The four strokes are explained here to understand how it works.

http://en.wikipedia.org/wiki/Internal_combustion_engine

http://en.wikipedia.org/wiki/Heat_of_compression

http://en.wikipedia.org/wiki/Combustion

http://en.wikipedia.org/wiki/Diesel_fuel

http://en.wikipedia.org/wiki/Combustion_chamber

http://en.wikipedia.org/wiki/Thermal_efficiency

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Suction Stroke or Intake The intake valve opens, and fresh air (containing no fuel), is drawn into the cylinder.

Compression Stroke

As the piston rises, the air is compressed, causing its temperature to rise. At the end of the compression stroke, the air is hot enough to ignite fuel.

Fuel Injection

Near the top of the compression stroke, the fuel injector drives fuel into the cylinder. The fuel immediately ignites upon contact with the hot compressed air.

Power Stroke

As the fuel burns, the gas in the cylinder heats and expands, driving the piston.

Exhaust Stroke The exhaust valve opens, and the exhaust is driven out of the cylinder.

Valve detail

The valves are operated by a variety of mechanisms on diesel and four stroke engines. The engine illustrated here features dual overhead camshafts, sometimes abbreviated DOHC. These are usually driven by a chain or cog belt.

General Maintenance of Diesel Engines:

1) The Engine Oil has to replace periodically.

2) The oil filters, air filters, diesel filters has to cleaned or replaced regularly.

3) The coolant oil or water should be maintained up to the top of the radiator.

4) The starting battery should be on full charge condition, for this a use separate

charger.

ALTERNATORS Alternators or a.c generators is a generator which gives out electrical energy in the

form of alternating current (a.c.). It works on the Faraday’s laws of electromagnetic

induction.

1) Whenever a conductor cuts the magnetic flux an emf induced in that conductor.

2) The induced emf is proportional to the rate change of flux linkages.

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An alternator consists of 2 basic elements namely:

Stator

Rotor(rotating element)

When the rotor is rotated by the prime mover the stator winding or conductors are cut by

the magnetic flux of the rotor poles.

Hence, an e.m.f is induced in the stator conductors because the rotor poles are alternating

e.m.f in the stator conductors. The frequency of the induced e.m.f is given by f=PN/120 Hz

where ‘p’is the total number of magnetic poles &’n’ is rotating speed at the rotor in r.p.m.

The direction of induced e.m.f can be found by applying Fleming right hand rule.

PARTS OF ALTERNATORS:-

An alternators consists armature windings mounted on a stationary element called STATOR

& field windings on a ROTAR ELEMENT

A ) Stator:-It consists of a cast-iron frame which supports the laminated armature core

having slots on its inner periphery for housing slots on the 3-phase winding.

b) ROTOR:-These are 2 types:-

i) SALIENT POLE TYPE

ii) NON-SLIENT TYPE

SALIENT POLE TYPE:- It is like flywheel which has a large number of alternator north

&south poles bolted to it. The magnetic poles are excited by a small d.c generator

mounted on the shaft of the alternator itself. These rotors are used in low & medium

speed. This speed is from 100-750 rpm.

Non Salient Pole Rotor: It is in round long cylindrical shape and the windings are placed by cutting

groves in to the cylinder. Due to not having projected poles it can with stand high speeds and can

designed up to 3000 rpm.

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At Kodad MBM there are two alternators are installed with a capacity of 160 kVA each (make: KEL).

Their speed is 1500 rpm, no. of poles are 4, type of rotor is non-salient pole.

The excitation DC generator was equipped on the same shaft and AVRs for stabilizing the output of

alternators are also equipped on the generator.

The prime movers of alternators are Diesel Engines.

BUS BAR CONTROL PANEL

In electrical power distribution, a bus bar is a strip or bar of copper, brass or aluminium that conducts electricity within a switchboard, distribution board, substation, battery bank, or other electrical apparatus. Its main purpose is to conduct a substantial current of electricity, and not to function as a structural member.

The cross-sectional size of the bus bar determines the maximum amount of current that can

be safely carried.

Main MV Panel:

At Kodad MBM the low tension (L T) supply from the power transformer is coming to Main

MV panel of the bus bar control room. For incoming supply there was equipped three ACBs

(air circuit breakers). Two ACBs are for two incomings and one is for bus coupler. Two sets

of over current and earth fault relays are equipped in the MV panel. The over current relays

passed a trip signal to the air circuit breakers whenever an over current drawn due phase to

phase short circuit fault occurred on load side or any equipment fault. Then the ACB trips

the LT supply automatically. If any flag shown fault in relays, then fault should be find out

first and should clear the fault and then only reset the relay and switch ON the ACB.

The earth fault relay passed trip signal to the ACB whenever any line conductor on load side

was earthed. Then ACB trips the circuit.

There are two buses installed separately on Main MV Panel for LT-1 and LT-2 supplies.

Whenever it is required to combine two buses for using PTR’s in parallel to gain high

capacity then another ACB is provided as bus coupler. The corresponding voltmeter and

ammeters are provided on the two bus bar panels. From this MV panel two LT supplies are

gone to another bus bar panel at which generator’s supply terminated.

Essential Panel:

This bus has a main facility of locking system. The APSEB switch must be opened

whenever the generator switches to be closed. If not opened the generator supply will

extends to APSEB lines which is very dangerous to the persons work on APSEB supply

systems and as well as the generator. That’s why a lock system is provided for generator and

APSEB supplies. Whenever generator supply to be taken the key of the lock should be get

from APSEB supply switch by opening it, otherwise the key can’t be get. Hence to get the

key the APSEB switch should be opened. With the key only the generator switch can be

http://en.wikipedia.org/wiki/Electrical_power_distribution

http://en.wikipedia.org/wiki/Copper

http://en.wikipedia.org/wiki/Brass

http://en.wikipedia.org/wiki/Aluminium

http://en.wikipedia.org/wiki/Electricity

http://en.wikipedia.org/wiki/Electric_switchboard

http://en.wikipedia.org/wiki/Distribution_board

http://en.wikipedia.org/wiki/Electrical_substation

http://en.wikipedia.org/wiki/Battery_(electrical)

http://en.wikipedia.org/wiki/Structural_load

http://en.wikipedia.org/wiki/Electric_current

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closed. For two generators and two LT supplies and two switch systems are provided on this

bus bar panel. From this bus bar panel the output supply for LT 1 and LT 2 are go to the

power plant room, AC plant room and building supply separately.

AVR ( Automatic Voltage Regulator)

A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level.

AVR is automatic voltage regulator which is nothing but stabilizer. In AVR there is motor which is

connected to the auto transformer with buck and boost transformer, as the voltage changes the

sensing microprocessor based card will sense and compare with the set value and give command to

the buck/boost transformer and motor rotate and set the required voltage automatically.

The Power Plant and the AC units are highly sensible to the supply voltage changes. If the supply

voltage is changed beyond predefined values the electronic equipments may get damaged. Hence in

Kodad Exchange two AVRs are installed at Power Plant (Which converts the AC to DC) and AC Plant

each of 45 kVA capacity. For the AVRs a separate panel provided with a facility switch to by-pass the

AVR when ever required.

POWER PLANT Any Telecommunication equipment required power supply of -48V DC, and the load

current will depends on the equipment. Power Plant in telecommunications is an equipment

to convert the AC power supply voltage to -48V DC. It should work as following

1) As a rectifier, it should convert AC power to DC.

2) It should Charge the battery sets and should compatible to them.

3) It should supply the load current required by the Exchange and other equipments.

4) It should have some protection features like opening of battery contacts, load

contacts.

5) It should have small modular structure instead of single large rectifier.

At BSNL Kodad the MBM and other connected equipments required total of 400A current

continuously at -48V DC.

For a continuous power supply two battery of 2000Ah sets are connected in paralled

to the exchange as shown below

The power plant is to convert 400 A load current to the exchange as well as charging current

to the battery sets.

Power Plant

1000A,

Exchange and

other loads

Two Battery sets,

2000 Ah each.

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Whenever the supply fail then the exchange takes is load current from the battery sets by

discharging them. Whenever Ac supply restored then the battery will take some charging

current from the power plant.

Hence Power plant has to supply 400A for exchange and another 400A for charging

batteries .

Hence power plant has to give a total of 800A for sometime up to the battery is

charged.

At kodad there was installed EXICOM company power plant with SMPS modules 10 no. Of

100 A modules was installed .

It is compatible with 2 no. of 2000 AH VRLA battery sets.

OPERATION MODES OF POWER PLANT:-

Float Mode: Whenever there is continuous AC supply the power plant has to give load

current for exchange and a small value of current for floating of batteries.

CHARGE MODE:-

After AC supply restored after power failure for some time, the power plant has to

supply exchange load current and as well as the charging current of batteries

up to they are fully charged .

The charging current is supply with constant current method as follows

POWER PLANT VOLTAGE BATTERY VOLTAGE CHARGING CURRENT

48.0 47.8 400A

48.0 47.9 200A

48.1 47.9 400A

48.1 48.0 200A

48.2 48.0 400A

. . .

. . .

55.0 54.9 200A

55.1 54.9 400A

55.1 55.0 200A

55.2 55.0 400A

53.7 Floating 53.70 5A

NOTE:-

CHARGE MODE MAXIMUM VOLTAGE IS── 55.2 V

FLOAT MODE VOLTAGE IS── 53.7 V

Suppose if 8*100A modules are working the power plant can give 800A

only. 400A for exchange and another 400A for battery are required. The voltage of power

plant raised up to it can give full modular capacity. Whenever the battery voltage is raise the

charging current will drop down. Then the power plant increases another step of voltage to

give 400A constant current. In this way the power plant brings the battery voltage up to the

fully charged voltage value which is present to it i.e. 55.2V and stopped. When it reaches

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55.2V it will comes down to float mode and gives 53.7 constant voltages. In this mode the

battery will take a minute current for floating.

BATTERY PROTECTION MODE: Whenever the battery is discharging for longer time, its voltage comes down. By

deep discharging of battery, its life will decrease tremendously. Hence a protection for

minimum voltage is set at 44.5V (24*1.85) whenever the battery is reaching to this value the

power plant acts its relay and opens the battery contact for protecting the battery. Then the

exchange will fail.

BATTERIES

In any communication equipments the Batteries and the corresponding Power plant are

known as the “Heart of the Communication System”, due to without these any system will not work

at all. So any communication engineer must have knowledge about the Batteries and power plants.

In general, recently at all communication equipments VRLA (Valve Regulated Lead Acid) batteries are

being used.

Basic Construction of LEAD ACID CELL:

A battery consists of a number of cells and each cell of the battery consists of

a) Positive and negative plates

b) Separators

c) Electrolyte

All contained in one of the many compartments of the battery container. Different parts of a lead acid battery are as under:

PLATES:

A plate consists of a lattice type of grid of cast antimonial lead alloy which is

covered with active material. The grid not only serves as a support for the fragile active

material but also conducts electric currents. Grids for the positive and negative plates are

often of the same design although negative plate grids are made some what lighter.

SEPERATERS:

These are thin sheets of a porous material placed between the positive and negative

plates for preventing contact between them and thus avoiding internal short circuiting of the

battery.

A separator must however be sufficiently porous to allow diffusion or circulation of electrolyte between the plates.

These are made of especially treated cedar wood, glass wool mat ,micro porous rubber, micro porous plastics and perforated p v c .

In addition to good porosity a separator must posses high electrical resistance and mechanical strength.

ELECTROLYTE:

It is dilute Sulphuric acid which fills the cell compartment to immerse the plates

completely.

CONTAINER:

It may be made of vulcanized rubber or mauled hard b rubber, moulded plastic,

ceramics, glass or celluloid. The vulcanized rubber containers are used for car service, while

glass container are superior for lighting plants and wireless sets.

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Celluloid container are mostly used for portable wireless set batteries. A single mono block type container with six compartment generally used for starting batteries. Details some of these parts are as follows.

BOTTOM GROOVED SUPPORT BIOCKS:

These are raised ribs either fitted in the bottom of the container itself.

There function is to support the plates and hold them in position and the same time protect them from short circuits that would other wise occur as a result fall of the active material from the plates on the bottom of the container.

CONNECTING BAR:

It is the lead alloy link which joins the cells together in series connecting the positive

pillar of one cell to the negative pillar of the next one.

TERMINAL POST OR PILLAR:

It is the upward extension from each connecting bar which passes through the

Cell cover for cable connections to an the positive terminal post.

VENT PIUGS OR PILLAR CAPS:-

These are made of polystyrene or rubber and are usually screwed in the cover .

There function is to prevent escape of electrolyte but allow the free exit of the gas These can be easily removed for topping up or taking hydrometer reading .

EXTERNAL CONNECTING STRAPS:-

These are the anti-ammonal lead alloy flat bars which connect the positive terminal posts of

the one cell to the negative of the next across top of the cover .

These are of very soiled construction especially in starting batteries because they have to carry very heavy current.

THEORY:-

Faradays law of electrolysis:-

First law:

The mass of ions liberated at an electrode is directly proportional to the quantity of electricity

i .e charge which passes through the electrolyte .

SECOND LAW:-

The masses of ions of different substances liberated by the same quantity of electricity are

proportional to their chemical equivalent weight.

ACTIVE MATERIALS OF A LEAD ACID CELL:-

Those substance of the cell which take active part in chemical combination and hence

observe or produce electricity during charging or discharging are none as active materials of

the cells.

The active materials of a lead acid cells are:- Lead peroxide(pbo2) for positive plate Sponge lead (pb) for negative plate Dilute sulpheric acid (H2SO4)as electrolyte

LEAD PEROXIDE:-

It is a combination of lead and oxygen is dark chocolate brown in color and is hard quite but brittle substance it is made up of one atom of lead(pb) and two atoms of oxygen (o2) and it its chemical formula is pbo2.As said earlier it forms the positive active material .

SPONGE LEAD:-

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It is pure lead in soft sponge or porous condition. Its chemical formula is pb and forms the negative active material.

DILUTE SULPHURIC ACID :-

It is approximately 3 parts water and one part is sulphuric acid. The chemical formula of

acid is H2SO4. The positive and negative plates are immersed in these solution which is known

as electrolyte. It is this medium through which the current produces chemical changes.

Hence the lead-acid cell depends for its action on the presence of two plates covered with PbO2 and Pb in a solution of dilute H2SO4 of specific gravity is 1.21 or near about.

Lead in the form of PbO2 or sponge Pb has very little mechanical strength , hence it is supported by plates of pure lead. Those plates covered with or otherwise supporting PbO2 are known as positive plate and those supporting sponge lead are called negative plate. The positive and negative plates are arranged alternatively and are connected to two common positive and negative terminals

These plates are assembled in a suitable jar or container to make a complete cell as discussed.

CHEMICAL CHANGES:-

DIS CHARGING:-

When the cell is fully charged its positive plate or anode is PbO2 (dark chocolate

brown) and the negative plate or cathode is Pb (slate gray ) When the cell discharges that is

it sends current through the external load then H2SO4 is dissociated in to positive H2(+) and

negative SO4(-) ions. As the current within the cell is flowing from cathode to anode , H2(+)

ions move to anode and SO4(-) ions move to the cathode .

At anode (PbO2) , H2 combines with the oxygen of PbO2 and H2SO4 attacks lead to form

PbSO4.

PbO2 + H2 + H2SO4 ─► PbSo4 + 2H2O

At the cathode (Pb) , SO4 combines with it to form PbSO4

Pb + SO4 ─► PbSO4

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It will be noted that during discharging:-

1) Both anode and cathode becomes pbso4 which is somewhat whitish in color. 2) Due to formation of water specific gravity of acid decreases. 3) Voltage of the cell decreases. 4) The cell gives out energy.

During CHARGING :-

When the cell is recharged the H2 ions move to cathode and SO4 ions go to anode and

the following changes take place:

AT CATHODE: PbSO4 + H2 ─► Pb + H2SO4

AT ANODE: PbSO4 + SO4 + 2H2O─► PbO2 + 2H2SO4

Hence the anode and cathode again becomes PbO2 and Pb respectively.

It will be noticed that during charging

1) The anode becomes dark chocolate brown in colour (PbO2) and cathode becomes gray metallic lead(Pb).

2) Due to consumption of water specific gravity of H2SO4 is increased. 3) There is a rising voltage. 4) Energy is absorbed by the cell.

The Voltages of a Lead Acid cell at various levels are as follows:

VRLA Batteries VRLA stands for valve-regulated lead-acid and is the designation for low-maintenance lead-acid rechargeable batteries. Because of their construction, VRLA batteries do not require regular addition of water to the cells. VRLA batteries are commonly further classified as:

Absorbent glass mat battery

Gel battery

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These batteries are often colloquially called sealed lead-acid batteries, but they always include a safety pressure relief valve. As opposed to vent (also called flooded) batteries, a VRLA cannot spill its electrolyte if it is inverted. Because VRLA batteries use much less electrolyte (battery acid) than traditional lead-acid batteries, they are also occasionally referred to as an "acid-starved" design. The name "valve regulated" does not wholly describe the technology; these are really "recombinant" batteries, which means that the oxygen evolved at the positive plates will largely recombine with the hydrogen ready to evolve on the negative plates, creating water—thus preventing water loss. The valve is strictly a safety feature in case the rate of hydrogen evolution becomes dangerously high. One result of this design is a much higher ratio of power to "floor space" than large, flooded type battery systems; another is a high-rate power capacity, though of relatively short duration. As a result, VRLA batteries are frequently employed in UPS (uninterruptible power supply) or other high-rate applications. Battery Rating: The most commonly using battery capacity rating is Ah (Ampere-Hours). Means the number of hours a battery can deliver a particular load current. For example if a battery can deliver a load current of 10 A for 5 hours its Ah capacity is 50 Ah. At Kodad MBM Exchange Two sets of batteries are being used.

1) Set A: Capacity : 2000Ah, make AMAR RAJA, having total 48 cells, two cells of 1000 Ah in parallel in each set and 24 those sets in series which will give an output of 48 V DC of 2000 Ah.

2) Set B: make Excide, Remaining things are same as above set A.

General Maintenance of VRLA Battery sets:

The given life of the battery sets are about 6 years from their date of install. By proper maintenance

of their charging power plant and batteries the life can extend further so many years. Since they

called as maintenance free batteries no special maintenance is required. But the following things

have to carry out regularly for increasing their life.

The battery contacts have to check out regularly for any heat generation by loose contacts, if so tighten the contacts.

Regularly take out the cell voltage readings discharging one hour or so to find out any fault cells after. If find so replace the fault cell immediately.

Apply petroleum jelly to all the contacts to avoid sparks between contacts. The charging and discharging should be verified. After discharging for some time the

corresponding power plant has to give the required charging current to it. If power plant not working properly the battery may not get charged. Hence failure may occur.

These voltage levels should be maintained accurately.

1) Charging limit: 55.2 V. Beyond this value the power plant voltage should drop to floating level. After reaching this value the battery should not prolonged this voltage for a long time, this will cause excessive gas production and internal pressure may raised.

2) Float Voltage: 53.7 V. After fully charged the batteries should be maintained at this constant voltage level.

3) Minimum Discharging Voltage: 45.0 V. We should not allow discharging the battery sets below this level. A serious damage may occur due to Sulphation. The Ah capacity may decrease permanently.

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Why –48 V DC being used?

The Positive terminals of the batteries are grounded for getting (negative) --48 V DC output.

Positive voltages cause comparatively more corrosion by cathode reaction in metal (that is underground copper wires) than negative voltages.

Negative voltages are safer for human body while doing Telecom activities. Lightning may cause positive voltages in the equipment circuitry. In that case, negative

voltages (lack of electrons) neutralize positive charges and prevent excessive heat. Negative voltage is safer for long telephone line for transmitting power trough it. Actually the earth is consider to be positive so we apply negative supply to our BTS so that

when lightening occurs the charge travels to the positive terminal like earth not to the BTS. if we apply positive to our equipment then both the equipment and the earth will be connected and our instrument can be damaged during lightening So negative polarity separates our BTS from earth.

One more thing is that all the digital equipments are configured to work on negative polarity.

AC PLANT Air conditioning is the process of altering the properties of air (primarily temperature and humidity) to

more comfortable conditions, typically with the aim of distributing the conditioned air to an occupied

space to improve thermal comfort and indoor air quality.

Refrigeration cycle

A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve,

3) evaporator coil, 4) compressor

http://en.wikipedia.org/wiki/Air

http://en.wikipedia.org/wiki/Temperature

http://en.wikipedia.org/wiki/Humidity

http://en.wikipedia.org/wiki/Thermal_comfort

http://en.wikipedia.org/wiki/Indoor_air_quality

http://en.wikipedia.org/wiki/Condensing_coil

http://en.wikipedia.org/wiki/Thermal_expansion_valve

http://en.wikipedia.org/wiki/Evaporator_coil

http://en.wikipedia.org/wiki/Gas_compressor

http://en.wikipedia.org/wiki/File:Heatpump.svg

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In the refrigeration cycle, heat is transported from a colder location to a hotter area. As heat

would naturally flow in the opposite direction, work is required to achieve this.

A refrigerator is an example of such a system, as it transports the heat out of the interior and

into its environment (i.e. the room).

The refrigerant is used as the medium which absorbs and removes heat from the space to be

cooled and subsequently rejects that heat elsewhere.

Circulating refrigerant vapour enters the compressor and is compressed to a higher

pressure, resulting in a higher temperature as well.

The hot, compressed refrigerant vapour is now at a temperature and pressure at which it

can be condensed and is routed through a condenser. Here it is cooled by air flowing across

the condenser coils and condensed into a liquid. Thus, the circulating refrigerant rejects heat

from the system and the heat is carried away by the air.

The condensed and pressurized liquid refrigerant is next routed through an expansion

valve where it undergoes an abrupt reduction in pressure. That pressure reduction results

in flash evaporation of a part of the liquid refrigerant, lowering its temperature.

The cold refrigerant is then routed through the evaporator. A fan blows the warm air (which

is to be cooled) across the evaporator, causing the liquid part of the cold refrigerant mixture

to evaporate as well, further lowering the temperature. The warm air is therefore cooled.

To complete the refrigeration cycle, the refrigerant vapour is routed back into the

compressor.

By placing the condenser inside a compartment, and the evaporator in the ambient

environment (such as outside), or by merely running an air conditioners refrigerant in the

opposite direction, the overall effect is the opposite, and the compartment is heated instead

of cooled.

Refrigerants:

Freon gas is mostly used refrigerant. Being it is Chlorofluorocarbon (CFC), it contribute to

global warming, and also deplete the ozone layer.

At Kodad MBM Exchange switch room there is an AC plant was equipped with three 3 - AC

packages of 7 TR each (Make: Feddors Lloyd). The CDOT switch has to maintain at the temperature

of 20 to 26 degrees as per its recommendations. Many electronic cards produces heat and may got

thermal run away and damaged if the heat is not transferred out properly. Therefore air conditioner

is compulsory for this.

General maintenance to AC plant:

The pressure of the refrigerant gas has to maintain at required level. If reduced check out

the total pipe lines, evaporator and the condenser coils for leakages and fill the new gas up

to the level.

The condenser is being at outside of the room the radiator has to clean with water regularly

for efficient operation.

http://en.wikipedia.org/wiki/Refrigerator

http://en.wikipedia.org/wiki/Refrigerant

http://en.wikipedia.org/wiki/Gas_compressor

http://en.wikipedia.org/wiki/Condensation

http://en.wikipedia.org/wiki/Condenser_(heat_transfer)



http://en.wikipedia.org/wiki/Flash_evaporation

http://en.wikipedia.org/wiki/Evaporator_coil

http://en.wikipedia.org/wiki/Refrigeration_cycle

http://en.wikipedia.org/wiki/Chlorofluorocarbon

http://en.wikipedia.org/wiki/Ozone_depletion

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4.0 Quality control Customer service is the final product of BSNL. Quality Control means test and verify the final

products of an industry whether it satisfies the predefined values and customer required values or

not.

Being a commercial organisation Quality Control in BSNL means customer service up to the

mark of customer satisfaction.

In time provision of New Phone Connections, New Broadband Services, New WLL Phones,

New SIM cards & 3G Data cards, New leased lines and other services available promptly and are

being maintained with up to customer satisfaction and maintain fault rate is very less. For better

Quality Of Service BSNL implementing and strictly following some time limit standards for each and

every New Connection and Fault Rectification.

For an example for a Leased Line fault the time limit is 6 hrs. If any Fault occurs to any Bank

or other Leased Line circuit, the corresponding employees have to rectify the fault immediately

within 6 hours. If not reasons should be stated otherwise suitable actions will be taken by higher

officers.

Following Mahatma Gandhi Quotations are displayed in CSC of BSNL for employee’s

motivation.

“A customer is the most important visitor on our premises. He is not dependent on us. We are dependent on him. He is not an interruption in our work. He is the purpose of it. He is not an outsider in our business. He is part of it. We are not doing him a favor by serving him. He is doing us a favor by giving us an opportunity to do so.”

SAFETY Every Industry is guide and instructed to follow some safety procedures to protect their

equipment and as well as humans who works at the equipments.

BSNL also follows some safety procedures for personnel protection and equipment protection

like fire safety, earthing, electrical safety, lightning safety, cell radiation safety.

Fire safety :

If any fire produced at any equipment or in any room due to electrical short circuit or due to

any other reason it has to extinguish immediately. For this purpose some fire alarm systems are

installed and some fire fighting equipments are provided in the exchanges.

Fire Alarm System:

At Kodad MBM we find two fire alarm systems one is for 1st floor at which switch room and

AC plant are located and another one is at ground floor at which power plant, MDF, OFC room are

located.

http://www.goodreads.com/author/show/5810891.Mahatma_Gandhi

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They have connected to so many fire detectors which are placed at top of the various rooms.

The fire detectors will detect the fire or smoke in those rooms and automatically sends the signals to

the fire alarm panel and an alarm will produced with a large sound automatically.

Then the operators will be alerted and try to get the fire extinguished.

Fire fighting equipments:

Types of Fires

Not all fires are the same. Different fuels create different fires and require different types of fire extinguishing agents. Class A

Class A fires are fires in ordinary combustibles such as wood, paper, cloth, trash, and plastics. Class B

Class B fires are fires in flammable liquids such as gasoline, petroleum oil and paint. Class B fires also include flammable gases such as propane and butane. Class B fires do not include fires involving cooking oils and grease. Class C

Class C fires are fires involving energized electical equipment such as motors, transformers, and appliances. Remove the power and the Class C fire becomes one of the other classes of fire. Class D

Class D fires are fires in combustible metals such as potassium, sodium, aluminum, and magnesium. Class K

Class K fires are fires in cooking oils and greases such as animals fats andvegetable fats.

Types of Fire Extinguishers

Water and Foam - Class A fires only

Carbon Dioxide - Class B & C fires

Dry Chemical - Class B & C fires only

Wet Chemical – Class A, K, B and C depending on the sub ype.

Dry Powder - Class D or combustible metal fires

Water Mist - Class A fires

Cartridge Operated Dry Chemical - Class A, B, and C fires

At Kodad MBM there are provided so many Fire Extinguishers of CO2 type and foam type which are

suitable for class BC fires in each and every room of the Exchange.

In Engine alternator room there also provided some red buckets filled with sand.

Earthing : To keep any conductor at ZERO potential value the conductor should connect to the earth

terminal which is buried under the ground up to certain depth. It is called earthing. There

are different earthing procedures like are followed.

Earthing systems: 1) Pipe earthing, 2) Plate earthing, 3) Strip earthing

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A typical pipe earth electrode diagram

For equipment safety and personnel safety earthing is compulsory.

At Kodad MBM the following earthing are done with pipe earthing.

1) Earthing for +ve terminal of the battery sets. This is for getting --48 V DC.

2) Body earthing of all the metal racks, frames and all metal structures. This is for human

safety, who are working at equipments.

3) A separate earthing is provided for Lightning arrestors provide on the top of the building

and on the top of the BTS tower.

4) Neutral earthing at the transformers. It is to keep the neutral at zero potential.

Electrical safety: For human safety in the exchange premises, insulation mats are provided at all

the electrically charged equipments.

Safety shoes are provided to all the personals.

All the metal bodies of all the equipments are earthed perfectly to keep them at

zero potential.

Danger boards are displayed at all harmful voltage levels, indicating that voltage

level.

Lightning safety: Lightning arrestors and lightning conductors are provided and earthed for

safeguard the equipments, BTS towers and buildings.

Cell radiation safety: Safety boards are displayed as Non - ionising radiation zone, near the cell towers for

not entering the unauthorised public in to the zone.

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POLLUTANTS FROM BSNL There are four main pollutants occur from BSNL:-

Cell Radiation. Sound and smoke from engine alternator. E-Waste

CELL RADIATION:-. Cell phones emit radiofrequency energy, a form of non-ionizing electromagnetic radiation, which

can be absorbed by tissues closest to where the phone is held. The amount of radiofrequency energy a cell phone user is exposed to depends on the technology of

the phone, the distance between the phone’s antenna and the user, the extent and type of use, and the user’s distance from cell phone towers.

Propaganda is there this radiation can cause some serious health hazards like hearing loss, cancer and memory loss etc..

But this issue is still under research stage. Up to till now the organisations like International Agency for Research on Cancer, World Health Organization and National Library of Medicine are not certified these bad effects can happen to the human beings.

Sound and smoke from engine alternator:

The Engine Alternators produces heavy sound and smoke during their operation which causes some disturbance to the surrounding people. Due they are running in only power failure hours the effect is minute. But now a days those Engine Alternator sets are manufactured with advanced technologies to minimise the sound and smoke.

E-Waste: E Waste is discarded Electrical and Electronic Equipments (EEE). "E-waste" is a popular, informal name for electronic products nearing the end of their "useful life. "E-wastes are considered dangerous, as certain components of some electronic products contain materials that are hazardous, depending on their condition and density. The hazardous content of these materials pose a threat to human health and environment. Discarded computers, televisions, VCRs, stereos, copiers, fax machines, electric lamps, cell phones, audio equipment and batteries if improperly disposed can leach lead and other substances into soil and groundwater. Many of these products can be reused, refurbished, or recycled in an environmentally sound manner so that they are less harmful to the ecosystem. This paper highlights the hazards of e-wastes, the need for its appropriate management and options that can be implemented. Effects of E-Waste constituent on health

Source of e-wastes Constituent Health effects

Solder in printed circuit boards, glass panels and gaskets in computer monitors

Lead (PB) Damage to central and peripheral nervous

systems, blood systems and kidney damage. Affects brain development of children.

Chip resistors and semiconductors

Cadmium (CD)

Toxic irreversible effects on human health. Accumulates in kidney and liver. Causes neural damage. Teratogenic.

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Relays and switches, printed circuit boards

Mercury (Hg) Chronic damage to the brain. Respiratory and skin disorders due to

bioaccumulation in fishes.

Corrosion protection of untreated and galvanized steel plates, decorator or hardner for steel housings

Hexavalent chromium (Cr) VI

Asthmatic bronchitis. DNA damage.

Cabling and computer housing

Plastics including PVC

Burning produces dioxin. It causes Reproductive and developmental problems; Immune system damage; Interfere with regulatory hormones

Plastic housing of electronic equipments and circuit boards.

Brominated flame retardants (BFR)

Disrupts endocrine system functions

Front panel of CRTs Barium (Ba) Short term exposure causes:

Muscle weakness; Damage to heart, liver and spleen.

Motherboard Beryllium (Be)

Carcinogenic (lung cancer) Inhalation of fumes and dust. Causes

chronic beryllium disease or beryllicosis. Skin diseases such as warts.

Not only BSNL all the communication companies cause to produce a large quantity of E-Waste. The main reason may be said as Technology Advancement in Communications. By the change of technology the old equipments are scrapped and not being purchased by another company also. Hence E-wastes are produced. A major concern has to put on this disposal of E-Wastes.

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CONCLUSION

Engineering student will have to serve in the public and private sector industries and workshop

based training and teaching in classroom has its own limitation. The lack of expo sure to real life,

material express and functioning of industrial organization is the measure hindrance in the student

employment.

In the open economy era of fast modernization and tough competition, technical industries should

procedure pass out as near to job function as possible.

Practical training is one of the major steps in this direction. I did my training from BSNL, KODAD

which is one of the best known communication service provider companies of India. The training

helps me in gaining in depth knowledge of the working of telephone exchange, various technologies

of BSNL –Broadband, GSM, WIMAX, Wi-Fi, MLLN and optical fiber transmission and other

equipments installed in BSNL Exchange.

In the end, I hereby conclude that I have successfully completed my industrial training on the above

topics.

Thank You.

industrial training record bsnl kodad

Technology

anurag college of engineering

kodad acknowledgement

months bsnl training

practical training

training report

need of training

communication engineering

vocational training