Transcript of "Training report on telecom exchange2"
TRAINING REPORT ON TELECOM
SIX WEEK INDUSTRIAL TRAINING
BHARAT HEAVY ELECTRICALS LIMITED
RANIPUR, HARIDWAR (UTTARAKHAND)
Submitted To: Submitted By:
Mr. Vikas Singla Raghav Aggarwal
Dy. Manager, Tel B.Tech (ECE)
“An engineer with only theoretical knowledge is not a complete engineer.
Practical knowledge is very important to develop and apply engineering skills”.
It gives me a great pleasure to have an opportunity to acknowledge and to
express gratitude to those who were associated with me during my training at
I am very great-full to Mr Vikas Singlafor providing me with an opportunity
to undergo training under his able guidance.
Furthermore, special thanks to Mr P. K. Joshi for his help and support in
Haridwar. Last, but not the least, I would also like to acknowledge the
immense pleasure, brought about by my friends Prem , Munish , Naveen as
they pursued their training along with me. We shared some unforgettable
I express my sincere thanks and gratitude to BHEL authorities for allowing me
to undergo the training in this prestigious organization. I will always remain
indebted to them for their constant interest and excellent guidance in my
training work, moreover for providing me with an opportunity to work and
A Major Project Report
Mr RAGHAV AGGARWAL
In partial fulfilment for the award of the degree
BACHLEOR OF TECHNOLOGY
ELECTRONICS & COMMUNICATION ENGINEERING
SCHOOL OF ELECTRONICS AND COMMUNICATION
SHRI MATA VAISHNO DEVI UNIVERSITY
2. BHEL Haridwar – An Overview
3. BHEL – A Brief Profile
4. INTRODUCTION TO TELECOMMUNICATION
5.INTRODUCTION TO TELECOM EXCHANGE
6.COMPONENTS OF TELECOM EXCHANGE
6.3 LINE CARDS
6.4 JUNCTION LINES
10. FACILITY OF TELEPHONE
BHEL was established more than 50 years ago when its first plant was setup in
Bhopal ushering in the indigenous Heavy Electrical Equipment Industry in
India. A dream which has been more than realized with a well-recognized
track record of performance it has been earning profits continuously since
1971-72 and will achieve a turnover of Rs 134,000 crore for the plan year
2012, showing a growth of 50% in the plan. Bharat Heavy Electricals Limited
is country’s ‘Navratna’ company and has earned its place among very
prestigious national and international companies. It finds place among the top
class companies of the world for manufacture of electrical equipments.
BHEL caters to core sectors of the Indian Economy viz., Power Generation's &
Transmission, Industry, Transportation, Telecommunication, Renewable
Energy, Defence, etc. BHEL has already attained ISO 9000 certification for
quality management, and ISO 14001 certification for environment
management and OHSAS – 18001 certification for Occupational Health and
Safety Management Systems. The Company today enjoys national and
international presence featuring in the “Fortune International -500” and is
ranked among the top 10 companies in the world, manufacturing power
generation equipment. BHEL is the only PSU among the 12 Indian companies to
figure in “Forbes Asia Fabulous 50” list.
Probably the most significant aspect of BHEL’s growth has been its
diversification .The constant reorientation of the organization to meet the
varied needs in time with a philosophy that has led to total development of a
total capability from concepts to commissioning not only in the field of energy
but also in industry and transportation.
In the world power scene BHEL ranks among the top ten manufacturers of
power plant equipments not only in spectrum of products and services offered,
it is right on top. BHEL‘s technological excellence and turnkey capabilities
have won it worldwiderecognition. Over 40 countries in world over have
placed orders with BHEL covering individual equipment to complete power
stations on turnkey basis.
BHEL has a share of 59% in India’s total installed generating capacity
contributing 69% (approx.) to the total power generated from utility sets as of
March 31, 2012. The company has been exporting its power and industry
segment products and services for over 40 years. BHEL’s global references are
spread across 75 countries. The cumulative overseas installed capacity of
BHEL manufactured power plants exceeds 9,000 MW across 21 countries
including Malaysia, Oman, Iraq, the UAE, Bhutan, Egypt and New Zealand.
2. BHEL – An Overview
BHEL today is the largest Engineering Enterprise of its kind in India
with excellent track record of performance, making profits
continuously since 1971-72.
BHEL's vision is to become a world-class engineering enterprise,
committed to enhancing stakeholder value. The company is striving
to give shape to its aspirations and fulfil the expectations of the
country to become a global player.
BHEL business operations cater to core sectors of Indian Economy.
The greatest strength of BHEL is its highly skilled and committed
60,000 employees. Every employee is given an equal opportunity to
develop himself and grow in his career. Continuous training and
retraining, career planning, a positive work culture and
participative style of management all these have engendered
development of a committed and motivated workforce setting new
benchmarks in terms of productivity, quality and responsiveness.
3. BHEL – A BRIEF PROFILE
BHEL is the largest engineering and manufacturing enterprise in India in the
energy related infrastructure sector today. The wide network of BHEL's 14
manufacturing division, four power Sector regional centres , over 150 project
sites, eight service centres and 18 regional offices, enables the Company to
promptly serve its customers and provide them with suitable products, systems
and services – efficiently and at competitive prices. While the company
contributes more than 75% of the national grid, interestingly a share of 45%
comes from its single unit. And this is none other than BHEL-HARIDWAR
Installed equipment for over 90,000MW of power generation--- for
utilities captive and industrial users.
Supplied over 2, 25,000 MVA transformer capacity and other equipment
operating in transmission and distribution network up to 400 kV (AC &
Supplied over 25,000 motors with drive control systems to power
projects, petrochemicals, refineries, steel, aluminium, fertilizers, cement
Supplied Traction electrics and AC/DC locos to power over 12,000 kms
Supplied over one million valves to power plants and other industries.
4.INTRODUCTION TO TELECOMMUNICATION
Telecommunication is communication at a distance by technological means,
particularly through electrical signals or electromagnetic waves
Early telecommunication technologies included visual signals, such as beacons,
smoke signals, semaphore telegraphs, signal flags, and optical
heliographsOther examples of pre-modern telecommunications include audio
messages such as coded drumbeats, lung-blown horns, and loud whistles.
Electrical and electromagnetic telecommunication technologies include
telegraph, telephone, and teleprinter, networks, radio, microwave
transmission, fibre optics, communications satellites and the Internet.
The conventional telephone now in use worldwide was first patented by
Alexander Graham Bell in March 1876 that first patent by Bell was the master
patent of the telephone, from which all other patents for electric telephone
devices and features flowed. Bharat Sanchar Nigam Limited (abbreviated
BSNL) is an Indian state-owned telecommunications company headquartered
in New Delhi, India. It is the largest provider of fixed telephony and fourth
largest mobile telephony provider in India, and is also a provider of broadband
services. However, in recent years the company's revenue and market share
plunged into heavy losses due to intense competition in the Indian
BSNL is India's oldest and largest communication service provider (CSP). It
had a customer base of 95 million as of June 2011. It has footprints throughout
India except for the metropolitan cities of Mumbai and New Delhi, which are
managed by Mahanagar Telephone Nigam (MTNL).
The first commercial telephone services were set up in 1878 and 1879 on both
sides of the Atlantic in the cities of New Haven, Connecticut, and London,
BHEL also caters to telecommunication sector by way of small, medium and
large switching system.
5. INTRODUCTION TO TELEXCOME EXCHANGE
A telephone exchange is a telecommunications system used in the public
switched telephone network or in large enterprises. An exchange consists of
electronic components and in older system also human operators that
interconnect (switch) telephone subscriber lines or virtual circuits of digital
systems to establish telephone calls between subscribers.
In the public telecommunication networks a telephone exchange is located in a
central office (CO), typically a building used to house the inside plant
equipment of potentially several telephone exchanges, each serving a certain
geographical exchange area. Central office locations are designating a facility
from which a telephone obtains dial tone. For business and billing purposes,
telephony carriers also define rate centres, which in larger cities may be
clusters of central offices, to define specified geographical locations for
determining distance measurements
For corporate or enterprise use, private telephone exchanges are often
referred to as private branch exchanges. They are installed in enterprise
facilities, typically collocated with large office spaces or within an
organizational campus to serve the local private telephone system and any
private leased line circuits. Smaller installations might deploy a PBX or key
telephone system in the office of a receptionist.
In the U.S. and Canada, the Bell System established in the 1940s a uniform
system of identifying each telephone exchange with a three-digit exchange
code, or central office code that was used as a prefix to the local telephone
station number. All exchanges within a larger region, typically aggregated by
state, were assigned a common area code. With the development of
international and transoceanic telephone trunks, especially driven by direct
customer dialling, similar efforts of systematic organization of the telephone
networks occurred in many countries in the mid-20th century.
5.TYPE OF EXCHANGES
MAX (Main Automatic Exchange)
PABX (Private automatic branch exchange)
BHEL has established MAX and PABX exchanges in Haridwar Unit with
calibration with BSNL
5.1MAX (Main Automatic Exchange)
A MAX is) is a telephone system within an enterprise that switches calls between enterprise
users on local lines while allowing all users to share a certain number of external phone
lines. The main purpose of a MAX is to save the cost of requiring a line for each user to the
telephone company's central office.
The MAX is owned and operated by the enterprise rather than the telephone company
(which may be a supplier or service provider, however). Private branch exchanges used
analog technology originally. Today, MAXs use digital technology (digital signals are
converted to analog for outside calls on the local loop using plain old telephone service
A MAX includes:
Telephone trunk (multiple phones) lines that terminate at the MOX
A computer with memory that manages the switching of the calls within the MOX and in
and out of it
The network of lines within the MAX
A console or switchboard for a human operator (optional)
In some situations, alternatives to a MAX include centrex service (in which a pool of lines are
rented at the phone company's central office), key telephone systems, and, for very small
enterprises, primary rate Integrated Services Digital Network (ISDN).
In MAX all users (phone no.) are not connected to PSTN directly. They are connected to
PSTN by an operator. In general we can provide different facility to different users like some
users are provided full connection (incoming and outgoing to outer network), normal
connection (incoming from outer network) and basic connection (for calling inside the own
In MAX if Mr X from other network wants to call Mr Y then his call is connected to operator
and operator connects the call to Mr Y’s NO. By this way call is completed. In this type of
exchanges has a very big disadvantage that if the Mr Y is not his place still caller has to pay
means money is charged without even call reached at his destination.
Initially, the primary advantage of MAXs was cost savings on internal phone calls: handling
the circuit switching locally reduced charges for local phone service. As MAXs gained
popularity, they started offering services that were not available in the operator network,
such as hunt groups, call forwarding, and extension dialling
It is also famous by the name of intercom
BHEL had established MAX in the beginning but it is now replaced by a PABX
5.2 Private automatic branch exchange
A private automatic branch exchange (PABX) is an automatic telephone switching system within
a private enterprise. Originally, such systems - called private branch exchanges (PBX) - required
the use of a live operator. Since almost all private branch exchanges today are automatic, the
abbreviation "PBX" usually implies a "PABX."
Lucent Technologies, Northern Telecom (NORTEL), Rolm/Siemens, NEC, GTE, Intecom,
Fujitsu, Hitachi and Mitel are among the larger manufacturers of PABX.
In BHEl Haridwar a PABX exchange is established with calibration with BSNL. Four thousand
numbers are provided to BHEL starting with 1,2,4,5 of ten thousand numbers (0000 –
9999).we can connect a call in BHEl to specific number by dialling Haridwar std code (01344)
The remaining numbers are either provided to other companies or reserved for future
usage. The call reaches its destination with going through operator so it is cost efficient
6. COMPONENTS OF TELECOM EXCHANGE
6.1 MAIN DISTRIBUTION FRAME (MDF):
MDF is a media between switching network and subscriber’s line. It distributes wires in
different areas and the wire containing switching room and subscriber’s line.
MDF has following components:
No of equipments
Wires and cables
6.2 Intermediate distribution frame
An intermediate distribution frame (IDF) is a distribution frame in a central office or customer
premises, which cross-connects the user cable media to individual user line circuits and may
serve as a distribution point for multipair cables from the main distribution frame (MDF) or
combined distribution frame (CDF) to individual cables connected to equipment in areas remote
from these frames.
IDFs are used for telephone exchange central office, customer-premise equipment, wide area
network (WAN), and local area network (LAN) environments, among others.
In central office environments the IDF may contain circuit termination equipment from various
auxiliary components. In WAN and LAN environments IDFs can hold devices of different types
including backup systems (hard drives or other media as self-contained, or as RAIDs, CD-ROMs,
etc.), networking (switches, hubs, routers), and connections (fiber optics, coaxial, category
cables) and so on.
6.3 Line card
A line card or digital line card is a modular electronic circuit on a printed
circuit board that interfaces with a telecommunications access network.
A line card typically interfaces the twisted pair cable of a POTS local loop to
the public switched telephone network (PSTN). Telephone line cards perform
multiple tasks, such as analog-to-digital and digital-to-analog conversion of
voice, off-hook detection, ring supervision, line integrity tests, and
other BORSCHT functions. In some telephone exchange designs, the line cards
generate ringing current and decode DTMF signals. The line card in
a subscriber loop carrier is called a subscriber line interface card (SLIC).
Northern Telecom World Line Card NT6X17BA, circa 1995
A line card can terminate a line supporting
voice POTS service, ISDN service, DSL service, or proprietary ones. Some line
cards are capable of terminating more than one type of service.
Since an access network element is usually intended to interface many users
(typically a few thousand), some exchanges have multiple line terminations
per card. Likewise, one network element can have many line cards
6.3 junction lines
These are the traditional telephone lines made from copper wire which is also
analogue switchboard telephone lines.
Even though they are analogue, they work very effectively they work very effectively
and are the most common PABX telephone
Analog telephone lines transmit voice as electrical signals. When you speak into the
handset of your phone, the microphone converts the sound waves into analog electrical
waves. These waves propagate over the telephone line to their destination. The receiving
phone then converts the electrical signals back into sound waves through the speaker of
Other names for analog telephone lines:
Analog telephone lines are referred to in a variety of ways. Here are some of the terms
you may hear from an installation professional or a service provider
C.O. Line – Refers to the fact that the line connects you to the Central Office
Copper Line – Refers to the historical medium that carries analog signals, namely copper
POTS Line – Plain Old Telephone Service
Analog Line – Refers to the analog electrical signal used to transmit voice
Good points to remember about analog telephone lines are that
One phone number is associated with one line
One line can handle one conversation at a time; when the line is in use, a busy
signal is heard
DLC eliminates the need for these remedies by extending out closer to the customer the
line card which digitises the voice signal for use by the PSTN. Once the voice signal is
digitised, it is easily manipulated and is no longer subject to the vagaries of the analog
loop caused by distance, impedance, attenuation and noise
7. Digital loop carrier
A digital loop carrier (DLC) is a system which uses digital transmission to extend
the range of the local loop farther than would be possible using only twisted
pair copper wires. A DLC digitizes and multiplexes the individual signals carried by
the local loops onto a single DataStream on the DLC segment.
Reasons for using DLCs:
Subscriber Loop Carrier systems address a number of problems:
Electrical constraints on long loops.
Insufficient available cable pairs.
Cable route congestion (inability to add cable due to lack of space, particularly in urban
street, bridge, and building conduit)
Construction challenges (in areas of difficult terrain) when limited cable pairs are
Expense due to cable cost and the associated labour-intensive installation work
In a typical configuration, DLC remote terminals are installed in new neighbourhoods or
buildings as a means of reducing the labour and complexity of installing individual local
loops from the customer to the central office (CO). A fibre optic cable or several copper
pairs for the whole system from the CO to the DLC remote terminal replace the
individual pair previously needed for each loop. DLC remote terminals are typically
stored in Serving Area Interfaces–metal cabinets alongside or near roadways that
overlie communications rights-of-ways.
With the growth in popularity of digital subscriber line (DSL) and the benefits provided
by shorter metallic loops used with DLC systems, digital loop carriers are sometimes
integrated with digital subscriber line access multiplexers (DSLAM), both systems
then taking advantage of the digital transmission link from the DLC to the CO.
8. Fiber-optic communication
Fiber-optic communication is a method of transmitting information from one place to
another by sending pulses of light through an optical fiber. The light forms an
electromagnetic carrier wave that is modulated to carry information. First developed in
the 1970s, fiber-optic communication systems have revolutionized the
telecommunications industry and have played a major role in the advent of the
Information Age. Because of its advantages over electrical transmission, optical fibers
have largely replaced copper wire communications in core networks in the developed
The process of communicating using fiber-optics involves the following basic steps:
Creating the optical signal involving the use of a transmitter, relaying the signal along
the fiber, ensuring that the signal does not become too distorted or weak, receiving the
optical signal, and converting it into an electrical signal.
Optical fiber is used by many telecommunications companies to transmit telephone
signals, Internet communication, and cable television signals. Due to much lower
attenuation and interference, optical fiber has large advantages over existing copper
wire in long-distance and high-demand applications. However, infrastructure
development within cities was relatively difficult and time-consuming, and fiber-optic
systems were complex and expensive to install and operate. Due to these difficulties,
fiber-optic communication systems have primarily been installed in long-distance
applications, where they can be used to their full transmission capacity, offsetting the
increased cost. Since 2000, the prices for fiber-optic communications have dropped
considerably. The price for rolling out fiber to the home has currently become more
cost-effective than that of rolling out a copper based network
Modern fiber-optic communication systems generally include an optical transmitter to
convert an electrical signal into an optical signal to send into the optical fiber, a cable
containing bundles of multiple optical fibers that is routed through underground
conduits and buildings, multiple kinds of amplifiers, and an optical receiver to recover
the signal as an electrical signal. The information transmitted is typically digital
information generated by computers, telephone systems, and cable television
9. Primary Rate Interface
The Primary Rate Interface (PRI) is a standardized telecommunications service level
within the Integrated Services Digital Network (ISDN) specification for carrying
multiple DS0 voice and data transmissions between a network and a user.
PRI is the standard for providing telecommunication services to offices. It is based on
the T-carrier (T1) line in the US and Canada, and the E-carrier (E1) line in Europe. The
T1 line consists of 24 channels, while an E1 has 32.
The Primary Rate Interface (PRI) consists of 23 64-kbit/s B-channels and one 64-kbit/s
D-channel using a T1 line, often referred to as "23B + D", (North American and Japanese
standard) or 30 B-channels and two D-channels using an E1 line (Europe/rest of world),
often referred to as "30B + 2D". A T1 Primary Rate Interface user would have access to a
1.472-Mbit/s data service. An E1 Primary Rate Interface user would have access to a
1.920 Mbit/s data service Larger connections are possible using PRI pairing. A dual PRI
could have 24+23= 47 B-channels and 1 D-channel (often called "47B + D"), but more
commonly has 46 B-channels and 2 D-channels thus providing a backup signalling
channel. The concept applies to E1s as well and both can include more than 2 PRIs.
Normally, no more than 2 D-channels are provisioned as additional PRIs are added to
The Primary Rate Interface channels are typically used by medium to large enterprises
with digital PBXs to provide them digital access to the Public Switched Telephone
Network (PSTN). The 23 (or 30) B-channels can be used flexibly and reassigned when
necessary to meet special needs such as video conferences. The Primary Rate user is
hooked up directly to the telephone company central office..
PRI provides a varying number of channels depending on the standards in the
country of implementation. In North America and Japan it consists of 23xB (B
channels (be/s). In Europe and Australia it is 30xB + 1xD on an E1 2.048 Mbit/s. One
timeslot on the E1 is used for synchronization purposes and is not considered to be
a B or D channel.
10. Facility of telephone
Facility to subscriber
A line can be made outgoing and incoming or outgoing
Hotline facility (immediate and delayed hotline)
Conference between more two subscribers
Automatic call back on busy
Malicious call identification
Facility to digital subscriber
Digital subscribers are provided with all facility provided to analog subscriber along with
following facility which are called ISDN services. An ISDN subscriber can use many
electronics devices with telephone devices and can use them for two or more simultaneous
calls for either
CALL TRANSFER FACILITY