An Overview ON
BSNL SUMMER TRAINING
VII SEM (ECE)
1. COMPANY PROFILE
3. ABOUT THE EXCHANGE
>TYPES OF FAULTS
8. PROCEDURE FOR HANDLING COMPLAINTS
Today, BSNL is the No. 1 telecommunication company and
the largest public sector undertaking of India and its
responsibilities includes improvement of the already
impeccable quality of telecom services, expansion of telecom
services in all villages and instilling confidence among its
Equipment which effects interconnected of telephones is
known as switching equipment.
The switching centre, which houses the terminating and
switching equipment is called telephone exchange.
ABOUT THE EXCHANGE
1. All telephone subscribers are served by automatic
2. Today’s automatic exchanges uses a pair of
One, running the program that provides services.
Second, monitoring the operation of the first, ready
to take over in a few seconds in the event of
Various exchanges present in BSNL are:
MAIN SECTIONS OF EXCHANGE:
There are three components of exchange:
MAIN DISTRIBUTION FRAME (M.D.F) :
- MDF means Main Distribution Frame. Local cable
contact at MDF .
- All types of cables out to the door contact
connection at MDF .
THE MAIN PARTS OF THE POWER ROOM ARE:
2. UPS (UNINTERRUPTED POWER SUPPLY)
3. CHARGING - DISCHARGING UNIT
4. INVERTER AND CONVERTER UNIT:
POWER PLANT :
SWITCHING ROOM :
Switch room consists of BM and CM
cabinets mounted in standard switch.
These cabinets are fastened to a switch
Room and interconnected by cables.
MAIN DISTRIBUTION FRAME
> The primary function of MDF is to remove
fault. It is also known as Fault Remove Section.
> The telephone numbers are also disconnected in
the MDF because of some specific reason.
ORGANISATION OF THE MDF
• Vertical side
• Horizontal side
RACK: -On the rack, the tags are situated. One rack is having eight
tags. The counting is done from up (0) to down (7).
TAGS: -Each rack consists of eight tags.
1 tag = 4 core
1 core = 4 bunch
1 bunch = 2 line
N.E.:-The word NE stands for the ‘NUMBER OF EQUIPMENT’.
It is used for testing number.
WEDGE: Wedge is used as a device for checking the ring. Wedge
is placed in jack strips, which is connected to telephone for
The horizontal side connected to the underground cable.
This cable is having 100 pairs. These pair is distributed
when we allot the telephone number to the subscriber.
Horizontal side is again subdivided in two parts:
One part is connected with the vertical side.
Another with the subscriber line by using 100 pair
CONSTRUCTION OF M.D.F:-
Main distribution frame is mainly divided in two
(1) Vertical Side or Line side.
(2) LEN side or Exchange side.
All the part from vertical side to the subscriber are
generally called outdoor section.:
1. One vertical has 10 tag blocks.
2. Each tag block has 10 rows and each row has 10 tags.
So each tag block has 100 tags.
3. Connection between vertical side & subscribers are
provided by jelly filled cables.
4. These wires are first terminated in cabinet box, then
according to requirements the group of the wires (e.g. 200
wires, 100 wires etc.) is terminated in pillar box
• All the parts from LEN to the exchange is called
• The connection of subscriber from exchange is
terminated on this side of MDF.
• In 1 tag block there are 128 tags. Each tag block is
divided in 4 segments. That is 0, 1,2 & 3 and in each
. DIFFERENT TYPES OF FAULTS:-
LOOP FAULT:-IF TWO WIRES ARE JOINED TOGETHER
BECAUSE OF IMPROPER CONNECTION,
STORMING AIR ETC.
EARTH FAULT:-IF TWO WIRES GET SCRAPE AT SOME PLACES
AND IF THIS WIRE COMES IN
CONTACT WITH TREE, PILLAR OR ANY METAL OBJECTS THEN
THIS TYPE OF FAULT OCCURS.
CABLE FAULT:-FOR OUTDOOR CONNECTIONS, JELLY FILLED
WIRES ARE USED WHICH ARE AFFECTED BY NATURAL
CAUSES SUCH AS RAIN, EARTHQUAKE ETC. AT SUCH TIME
THIS FAULT OCCURS.
DISCONNECT FAULT:-THIS TYPE OF FAULT OCCURS DUE TO
THE BREAKING OF WIRES BETWEEN THE VERTICAL SIDE &
ROTECTIVE DEVICES USED IN M.D.F
Gas Discharge Tube(G.D Tube)
The new switching systems are based on Stored Program
Control concept. The call processing programmers are
distributed over different control organs of the system and
are stored in ROM/RAM of the units Processor in the
control units .
It is a digital switching system.
The system supports all the existing signaling system
.The system has ‘auto recovery’ feature. When a
serious fault occur in control unit, it gives a message
to SMM (operation & maintenance unit).
•GLOBAL SYSTEM FOR MOBILE
Global system for mobile communication (GSM) is a
globally accepted standard for digital cellular
communication. GSM is the name of a standardization
group established in 1982 to create a common European
mobile telephone standard
GSM is a cellular network which means that mobile
phones connect to it by searching for cells in the
immediate vicinity. GSM operates in the 900 MHz
THERE ARE FIVE DIFFERENT CELL
SIZES IN A GSM NETWORK-
GSM : (SYSTEM ARCHITECHTURE)
This system structured hierarchically as shown:
It consist of one administrative region, which is
assigned to a MSC(Mobile Switching Center).
Each administrative Region is made up of atleast one
Location Area(LA). LA is also called the visited area.
An LA consists of several cell groups.
Each cell group is assigned to a base station
Cells of one BSC may belong to different LA’s.
BASIC BUILDING BLOCKS:
Mobile Station (MS)
Base Station (BS)
Mobile services Switching Center (MSC)
Operation and Maintenance Center (OMC)
Shannon’s Theory predicts the maximum amount of
information that can be transmitted over a channel
with given BW & SNR.
The optimum usage of given BW is obtained when the
signal are noise – like & min SNR.
Hence for increased capacity the choice is CDMA.
MEDIA : -
2. Co-axial Cable
3. Optical Fiber Cable(OFC).
PROCEDURE FOR HANDLING
Case--I Problem concerns a particular subscriber.
Case-II Quit a few numbers of telephone reported dead:
Telephone Held-Up ( No Dial Tone ):
> PERMANENT RING
> PERMANENT DIAL TONE
> PERMANENT BUSY TONE
> PERMANENT RING – TRIP
> SPEECH QUALITY POOR
> WRONG NUMBERS
> ONE WAY SPEECH
> RINGER CADENCE
Fibers of glass
Usually 120 micrometers in diameter
Used to carry signals in the form of light over
distances up to 50 km.
No repeaters needed.
INTRODUCTION TO OPTICAL
Core – thin glass center of the fiber where light
Cladding – outer optical material surrounding
Buffer Coating – plastic
coating that protects
EVOLUTION OF FIBER
1880 – Alexander Graham Bell
1930 – Patents on tubing
1950 – Patent for two-layer glass wave-guide
1960 – Laser first used as light source
1965 – High loss of light discovered
1970s – Refining of manufacturing process
1980s – OF technology becomes backbone of
long distance telephone networks in NA.
ADVANTAGES OF OPTICAL FIBRE
Higher Carrying Capacity
Less Signal Degradation& Digital Signals
AREAS OF APPLICATION
Local Area Networks
Optical Fiber Sensors
TYPE OF FIBERS
Optical fibers come in two types:
Single-mode fibers – used to transmit one
signal per fiber (used in telephone and cable TV).
They have small cores(9 microns in diameter) and
transmit infra-red light from laser.
Multi-mode fibers – used to transmit many
signals per fiber (used in computer networks).
They have larger cores(62.5 microns in diameter)
and transmit infra-red light from LED.
HOW DOES OPTICAL FIBRE
Total Internal Reflection.
Fibre Optics Relay Systems has