ACKNOWLEDGEMENT
I am grateful to the staff and management for letting me pursue my four weeks industrial training at the department of telecommunication (in the Transmission department) at their commercial in sector 34,CHD.
I am grateful for the explanation given to me by the staff of Transmission department and helping me become aware of the technology in the real world .The trainingI had received here has helped me immensely in understanding the practical concepts of communication.
I extend my heartfelt thanks to Mr.SANJAY AGGARWAL (D.G.M planning & transmission) & Mr. S.K. DHINGRA (D.E.P) for allowing me to undertake the training under their guidance.I also thank Mr. PAWAN SHARMA (S.D.E) for helping and guiding me at every stage.
This report would have been incomplete without the help of Mr. RAHUL(JTO Transmission) who gave a complete insight of Transmission.
I extend my gratitude to the entire staff of BSNL.It was a pleasure undertaking training in BSNL.
DEPARTMENT OFTELECOMMUNICATION
CONNECTING PEOPLE TOGETHER
FUNCTIONS Apart from policy making,the main functions of the Department Of Telecommunications (DOT) are planning, engineering, installation & operation of telecommunication services all over India & with other countries. The department is also responsible for grant of licenses to private sector operators for providing basic & value added services in various cities & telecom circles as per approved policy of government. The department also allocates frequency & manages radio communications in close coordination with the international bodies. It is also responsible for enforcing wireless regulatory measures & monitoring the wireless transmissions of all users in the country.
B.S.N.L is one such telecommunication department which provides with the facilities like cellular mobile telephone services, public mobile radio trunk, radio paging, remote area service etc.
INTRODUCTION TO B.S.N.L
On October 1,2000 the Department of Telecom Operations, Government of India became a corporation & was christened BHARAT SANCHAR NIGAM LIMITED(BSNL). Today BSNL is the No.1 Telecommunications Company & the largest Public Sector Undertaking of India & its responsibilities include improvement of the already impeccable quality of telecom services, expansion of telecom network, introduction of new telecom services in all villages & instilling confidence among its customers.
Today with a aprx. 43 million line capacity, 99.9% of its exchanges digital, nation wide Network Management & Surveillance system(NMSS) to control telecom traffic & nearly 3,55,632 route kms of OFC network, BSNL is a name to reckon with in the world of connectivity. Along with its vast customer base, BSNL’s financial & asset bases too are vast & strong. Consider the figures, as they speak volumes on BSNL’s standing:
- The telephone infrastructure alone is worth about Rs.1,00,000 crore (U.S.$21.2billion).
- Turnover of Rs.22,000 crores (US 4.6 billion)
MISSION OF BSNL IS-
“To provide the world class Telecom Services on demand using State-of-Art Technology for the value added Customers at
affordable price”.
SERVICES PROVIDED BY B.S.N.L. -
1.TARANG(WLL Mobile Service)-WLL is wireless in local loop. WLL is a communication system that connects customers to the Public Switched Telephone Network i.e. Landline, Mobile(GSM) and WLL(CDMA) using radio frequency signals as a substitute for conventional wires for all or part of the connection between the subscribers & the telephone exchange. It may be used for connecting remote & scattered rural areas, helping relieve congestion of connections, mobility without any airtime charge.
2.SANCHAR NET- Today, the internet has become a worldwide phenomenon providing better communication. Sanchar Net provides free all India roaming & enables it’s users to access their accounts from anywhere in country except in new Delhi & Mumbai.
3.CELLONE –BSNL produced India’s biggest cellular service,CELLONE(POSTPAID SERVICE) which brings cellular telephony to the masses. This ambitious service uses state-of-the-art GSM technology to attain global excellence & leadership in business. It serves the single objective, to provide better communication.
4.BFONE-Gone are the days when telephones use was restricted only to make & receive calls. BSNL offers phone plus services like Answering Machine Service(AMS), SMS on landline,, Call waiting, Hot line, Call transfer etc.
5.EXCEL-BSNL produced another cellular service, EXCEL which is a PREPAID SERVICE which brings cellular telephony to the masses. It serves the objective of providing better communication.
6 ISDN:-Integrated Service Digital Network Service of BSNL utilizes a unique digital network providing high speed and high quality voice, data and image transfer over the same line. It can also facilitate both desktop video and high quality video conferencing.
7.Leased lines and dotcom:-BSNL provides leased lines for voice and data communication for various application on point to point basis. It offers a choice of high, medium and low speed leased data circuits as well as dial-up lines. Bandwidth is available on demand in most cities. Managed Leased Line Network (MLLN) offers flexibility of providing circuits with speeds of nx64 kbps upto 2mbps, useful for Internet leased lines and International Principle Leased Circuits
The different divisions of the telephone exchange are:
Administrative department: Here, various administrative functions like employee database, new recruitments, transfers of employees, policies and important decisions are made,
Commercial department: Here, various commercial activities like applying for a new telephone, shifting of telephone, malicious call tracing etc are made,
Planning department: It has two parts:
Exchange planning:It handles the setting up of new exchanges after considering their need, their technology, their capacity, the BHCA (busy Hour Call attempts) of the area, etc
Cable planning: This handles the setting up of new cables according to the existing need using the best types available and making decisions like where to dig and install the cables using what equipment, etc.
Indoor department: This includes the staff and the technicians which are sitting in the exchange including those providing facilities like 197, etc
Outdoor department: This includes the staff that is employed to work outdoors of the exchange like linesmen, etc
TRA department: Here, the most important function is to meter the calls and to provide the bimonthly telephone bills so as to enable the department to earn revenue for its services, If the database in this department fails, all the existing records are lost, Data is stored in magnetic disks and tapes.
PHYSICAL CONNECTIVITY BETWEEN
SUBSCRIBER’S TELEPHONE
AND
TELEPHONE EXCHANGE
CABLE NETWORK USED
It consists of three types of copper cables.
- Primary Cable :-It is the cable, which is connected from line side of M.D.F. to the cabinet. It is an underground cable. It consists of particular number of secondary cables.
- Secondary Cable :-It is the cable, which is connected from cabinet to the pillers
- Distribution Cable :-It is the cable, which is connected from pillars to the distribution pole
.
- Drop wire :-It is a pair pf copper wire, which is connected from the distribution pole to the subscriber’s telephone.
Exchange & Main Distribution Frame(MDF) are connected physically to each other with the help of simple copper cables. From MDF, PRIMARY CABLES are laid upto the different CABINET locations, where cabinets are Elmira type boxes placed on the roadside.Now a days Cabinets are not used .These primary cables are pairs of wires eg.800 pairs given to a single cabinet, 1200 pairs to another & so on. From the Cabinet, SECONDARY CABLES are laid. These are connected to the PILLARS of different locations. Secondary cables are the further divisions of the already laid primary cables of a Cabinet eg. out of 800 PC, 400 pairs are given to one Pillar, 200 to another & 100 to other Pillar location. From the Pillar DISTRIBUTION CABLES are spread to DISTRIBUTION POLES (DP), different number pairs are given to different locations of DP eg.out of 200 divisions of 50,100,20,20,10 are made according to the requirements of the locations to which connection is given. The different cables laid up till now are all underground connections. The DP consists of CT BOX, through which DROP WIRE is attached from one end & to the subscriber’s telephone on the other end, hence giving us the connectivity.
EXCHANGE BLOCK LAYOUT-The various divisions associated within Telephone Exchange are shown in following block
diagram.
TELEPHONE EXCHANGE
M.D.F. & O. C.S. UNIT:-
DEPARTMENT 1
COMPUTER ROOM
The staff supervised us around the computer room showing us the various functions performed by the computer. The various computer terminals are:-
- MAIN COMPUTER
- I.V.R.S
- MAIN COMPUTER
With the help of this computer terminal we are able to keep check on the total no. of telephones present in a certain exchange.
- I.VR.S.:-
With the help of this computer, which is called the I.V.R.S. (Interactive Voice Response System), we can note down the incoming calls of complaints of faulty telephones. This system can book all the complaints without any external interference.
The voice response equipment, available as an option is used for services that indicate charging information, change of directory number to calling subscribers’ etc. The voice response equipment can compose messages for their services.
3.MDF –MAIN DISTRIBUTION FRAME
The main function of M.D.F is to connect the exchange side with the line side. It is made up of two sides that is the Exchange side and the Line side. Basically the MDF consistsof CT boxes .These CD block which help in connecting the Exchange as well as the Subscribers.MDF is mainly a maintenance division which checks & repairs the faults.
BASIC OVERVIEW OF MDF-
EXCHANGE SIDE:-
Exchange side is the where all the cable wires are connected coming from the exchange.
LINE SIDE:-
Line side the side where all the wires are connected coming from the subscriber’s place.
JUMPER
EQUIPMENT VERTICAL
NUMBER NUMBER
*EUIPMENT NO.-Various equipment no.’s into various exchanges like
1. FETEX-no. 66 & 64
2. OCB-no. 62
3. E10B-no. 60 & 61
Equipment no. can be same as these are taken from one exchange.There is different NE or LL for different lines which are allotted by exchange.
*VERTICAL NO.It is used to terminate the primary wire and used to connect the exchange with outside line.There are 48 verticals given no.’s like
V1,V2,V3-----V48 in Sec34 MDF. Each vertical has 10 C.T. boxes & each C.T. box has 100 numbers. Thus from single vertical 1000 telephone connections can be given. Vertical no are always different.
*JUMPER-It is a red & white wire using ground tool connecting equipment number (NE or LL) to the vertical number.
NE : - Equipment Number
LL : - Line Location
*HEAT COIL-It is used on the vertical side so that if some short circuit occurs, then it prevents extra current which may otherwise damage the lines.
We give the following commands on the computer when there is any faultin the line
ROT (Right on Test) :- The phone was working right when the test was being conducted.
Earth :-When the resistance is less than 250 K/amp then we write that the lines are earthed and we enter E as code.
FP-Foreign Potential :- When the DC Voltage is less than DV i.e. – 45 V or 50 V then we give the name of fault as FP.
BK (Break) :- When there is a capacitance less then the name of the fault is given as BK.
Contact :- This fault occurs when both the wires are connected with each other.
SWITCH ROOM:-
DEPARTMENT 2
E-l 0 B (SWITCH ROOM)
ESTABLISHMENT OF E10B
The first E-l0-B system (a training model) was commissioned at ALTCC, Ghaziabad in July 84. The first commercial E-I0-B system was setup at Bombay in April 85 supporting 10,000 lines. Also 22,000 lines of digital TAX (E-I0-B type) have been installed at 16 stations all over the country.(The first at Agra in Feb. 87)
Palaghat (Kera1a) unit of ITI manufactures E-I0-B TAX equipments. Another ITI factory at MANKAPUR in GONDA (UP) produces annually 500,000 E-l 0B local lines
EVOLUTION OF E-10B SYSTEM
The predecessor of E-10B is the E-10A system developed in France in early Seventies. Based on the structure of E-10A, a more powerful\system with a significantly higher call handling / traffic capacity was developed in early 80's. The first E-10system was commissioned at BREST in FRANCE. The system has many versions. Tile INDIAN version is the 384 PCM versions and can handle max traffic capacity of 4000 erlangs. The BHCA is 1,90,000.
APPLICATIONS OF THE E-10-B SYSTEM
(a) LOCAL EXCHANGES
These exchanges terminate local subscriber lines and are connected to other exchanges in the local network. The limit of max traffic handling capacity is 4000 erlangs. Within this, any proportion of subscribers and junctions is possible.
(b) LOCAL, TRANSIT, TANDEM EXCHANGES
E-10B system can be used to carry pure transit traffic. Here, subscribers line providing terminating equipments will not be provided. Only equipments needed for connecting junctions will be provided.
(c) TAX
Here, the system provides for termination of long distances circuits. Digital Tax’s has a max capacity of 11,000 lines (o/g and I/g) in 384 versions.
(d) LOCAL CUM TRANSIT OR TAX
The facilities of local and transit can be combined.
FACILITIES AND SERVICES TO THE SUBSCRIBER
(I) Call forwarding
(2) Short code Dialing
(3) Malicious call tracing
(4) Conference calls
(5) Call waiting
(6) Detailed billing
(7) Automatic alarm call
(8) Barred access
(9) Hotline facility
(10)Pushbutton telephone
(11) Last number redial
Because of its modular structure, E-10-B can be expanded to meet its demands and new services can be introduced with modification of software.
Features of E10-B system
The system is based on these features.
(I) Stored program control
(2) TDM digital switching
(3) PCM principals and techniques
(4) Segregation of switching and management facilities.
(5) Distributed control using dedicated microprocessors,
e.g. 8085, ELS-48
(6) Centralized management for a group or E-1 0-B exchanges.
Stored Program Control
Control functions relating to call processing are carried out by execution of program instructions stored in the memory of computers. In electromechanical systems, these functions are hardware based. In E-l0B, these arc software based.
TDM Digital Switching
The system switches signals to digital form. Analog signals are converted to TDM multiplexed digital signals, prior to switching.
PCM Principles
Systems have been developed for 30 channels PCM corresponding to Relevant CCITT recommendations.
Segregation b/w switching and management functions
Switching functions like reception of dialed digits, the storage, the analysis, routing of the call etc. arc performed by the control unit in the exchange, which has a decentralized architecture, employing dedicated processors. Functions like subscribe lines and circuit group management, faults and alarm management etc. are done by a separate mini computer, located at a centralized operation and maintenance center (OMC), which is common for a number of E-10-B exchanges. OMC and switching centers are interconnected by PCM links. They could be in the same- premises or far apart.
Distributed control
Call handling and call processing functions like scanning of subscriber lines, detection of loop status, reception and storage of digits etc. are distributed over functional units. Dedicated processors like Intel 8085 and dedicated mini computers like ELS-48 handle them.
Centralized management for a group of E – 10 B exchanges
The O&M functions for a group of E-I 0-8 exchanges (upto a maximum of 6 exchanges or '80,000 lines) are carried out by single OMC, which is connected to various exchanges by PCM links.
The E-IO-8 exchange consists of three blocks:
a. Connection units
b. Switching networks
c. Control units
Connection Units
They act as an interface between external environment (i.e. subscribers and trunks) and central units. Units, which manage the generation and transmission of, digitalized tones and frequencies and dissemination of recorded announcements to subscribers are also called connection units.
Switching networks (CX)
This is a TDM switching network having a three stage time-space-time architecture. It uses four wires switching (4W) for connecting time slots of calling and called parties.
Control Units
The control unit handles telephone call setup, supervision, clear down and charging functions.
Specifications of E-10B:-
I. Number of switchable PCM links: 384
2. Processing capacity: 1,90,000BHCA
3. Traffic handling capacity: 4000erlangs
4. Subscriber exchange: 45,000 lines & 5000 circuits
SYSTEM FEATURES:-
I. Time division multiplexing
2. PCM to CCITT standards
3. 2 Mbit/s PCM link
4. 30 telephone channels per PCM link
5. 8 bits per telephone channel
6. Stored program control
7. Dedicated processors for program control
8. Non dedicated processor for operation functions
SUBSCRIBER LINE
1. Dial or pushbutton VF telephone
2. Maximum loop resistance inclusive of telephone set 2400 ohms
3. Ringing current: 80 V, 25 and 50 Hz
ENVIRONMENTAL CONDITIONS
Exchange:
1. Ambient temp of air drawn into racks: 18 - 20 deg C
2. Relative humidity: 30 - 70 %
Satellite exchange:
1. Ambient temp: 5 -35 deg C
2. Relative humidity: 20 - 80 %
DIMENSIONS OF E-10B:-
1. Rack dimension: height: 2 mt, width 0.75 mt, depth 0.5 mt, Distributive floor loading, less than 500 kg/sq. mt
2. Floor area: 45,000 lines subscriber exchange = 154 sq. mt
11,000 lines subscriber exchange = 90 sq. mt
POWER SUPPLY REQUIREMENTS:-
1. Exchange and satellite exchange = -48 V
2. OMC: 220 V, 50 Hz
3. Power supply current online: 23 - 60 mA
4. Loop resistance: 1500 to 2400 ohms
CALL PROCESSING IN E-IO B EXCHANGE
The following types of call processing has been described:
1) Local call
2) I/C call
3) O/g call
A call is processed in the following four stages:
1) Pre-selection
2) Selection
3) Connection and charging
4) Release
PURPOSE OF MDF AND DDF IN E-10B EXCHANGE
E-10B switching system is a digital switching system and accepts both analog and digital signals. The signals from subscriber are analog whereas the trunk signals are digital (if coming from analog source, these are converted into digital 30 channel PCM signals and then fed to switch room).