BHARAT SANCHAR NIGAM LIMITED (BSNL) UNNAO ,UTTAR PRADESH
A TRAINING REPORT BY GAURAV SINGH ECE-7421
ACKNOWLEDGEMENT
I would like to express my deep gratitude to the following people, without their help and support the purpose of training can not be accomplished. Mr. D.K.Sharma,sub divisional officer, EWSD TAX Exchange, BSNL, Unnao,Uttar Pradesh. Mr. Sunil Bellani,junior telecomm. officer,EWSD TAX Exchange, BSNL, Unnao, Uttar Pradesh. Mrs. Chitra, Junior telecomm. officer, C-DOT Exchange, BSNL,Unnao, Uttar Pradesh. Mr. Ashok Bhatiya,telecomm. technical assistant,transmission department, BSNL,Unnao,Uttar Pradesh. Mr. Sachin Diwedi and Gaurav Diwedi, call center operators,BSNL, Unnao,Uttar Pradesh. Mr. Vibhav Nigam, operator in the exchange,BSNL,Unnao, Uttar Pradesh.
CONTENTS:1) Telephone Exchange an introduction 2) History of Telephone Exchange 3) How Exchange Works 4) Revolutionary changes in the working way of telephone exchanges 5) Manual Service Exchange 6) Automatic Exchange 7) Units of Exchange 8) Telephone System 9) Broadband and its Working 10) Pictorial presentation of set up of Broadband 11) An Introduction of GSM and its working
TELEPHONE EXCHANGE AN INTRODUCTION In the field of telecommunication, a telephone exchange or
telephone switch is a system of electronic components that connects telephone calls. A central office is the physical building used to house inside plant equipment including telephone switches, which make telephone calls "work" in the sense of making connections and relaying the speech information.
A PICTURE OF SWITCHBOARD
HOW EXCHANGE WORKS? When a calling party lifted the receiver, a signal lamp
near the jack would light. The operator would plug one of the cords into the
subscriber's jack and switch her headset into the circuit to ask, "number please? Depending upon the answer, the operator might plug
the other cord of the pair (the "ringing cord") into the called party's local jack and start the ringing cycle.
MANUAL SERVICE EXCHANGE With manual service, the customer lifts the receiver off-
hook and asks the operator to connect the call to a requested number. The operator connects the call by plugging into the jack on
the switchboard. If the call is to another central office, the operator plugs
into the trunk for the other office.
Most urban exchanges were common-battery. In
common battery systems, the pair of wires from a subscriber's telephone to the switch (or manual exchange) carry -48VDC (nominal) from the telephone company end, across the conductors. The telephone presents an open circuit when it is on-
hook or idle. When the subscriber goes off-hook, the telephone puts a DC resistance. The buzzer and lamp would tell an operator the
subscriber was off-hook (requesting service).
AUTOMATIC EXCHANGES Automatic exchanges, or dial service, came into
existence in the early 1900 s. Before the exchanges became automated,
operators had to complete the connections required for a telephone call.
A telephone switch is the brains of an automatic
exchange. It is a device for routing calls from one telephone to another, generally as part of the public switched telephone network(PSTN). hook telephone condition, provides dial tone to that phone, receives the pulses or tones generated by the phone, and then completes a connection to the called phone within the same exchange or to another distant exchange.
The local exchange automatically senses an off
The exchange then maintains the connection until a party
hangs up, and the connection is disconnected. This tracking of a connection's status is called supervision. Additional features, such as billing equipment, may also be incorporated into the exchange. In Bell System dial service, a feature called automatic
number identification (ANI) was implemented . In manual service, the operator knows where a call is
originating by the light on the switchboard's jack field. In early dial service, ANI did not exist. Long distance calls would go to an operator queue and the operator would ask the calling party's number, then write it on a paper toll ticket.
A PICTURE OF DIGITAL EXCHANGE
UNITS OF AN EXCHANGE
Computer Unit : It deals with additional services of the exchange to the customer with the help of computers. Power Plant: It feed proper power supply to exchange. In EWSD and C-COT Exchange -48 volt (D.C) is supplied. AC Plant: to maintain the continuous 24 degree Celsius to the digital switch (exchange). Main Distribution Frame (MDF): to connect digital switch (exchange) with the external environment (subscriber) i.e. it is the interface between subscribers and exchange. Antenna: It is an important part of exchange that maintains the signals for communication.
AN INTRODUCTION OF TELEPHONE SYSTEM
TELEPHONE SYSTEM The telephone ,commonly referred to as a phone, is a
telecommunications device that transmits and receives sound most commonly the human voice. Telephones are a point-to-point communication
system.
The device uses a microphone in the handset to convert the
sound waves to electrical signals, which are sent through the telephone network to the other phone, where they are converted back to sound waves by an earphone in the handset.
The telephone network, consisting of a worldwide net of
telephone lines, microwave transmission, cellular networks, communications satellites, and undersea telephone cables connected by switching centre, allows any telephone in the world to communicate with any other.
Each telephone line has an identifying number called its
telephone number. In order to initiate a telephone call, a conversation with another telephone, the user enters the other telephone's number into a numeric keypad on his phone.
BASIC PRINCIPLES AND ITS WORKING A traditional landline telephone system, also known
as plain old telephone service" (POTS), commonly handles both signalling and audio information on the same twisted pair of insulated wires. This system has been adapted for data
communication such as Telex, Fax and dial-up Internet communication. A twisted pair line is preferred as it is more
effective at rejecting electromagnetic interference (EMI) and crosstalk than an untwisted pair.
The telephone consists of an alerting device, usually a
ringer. A calling party wishing to speak to another party makes the phone into active state. The exchange indicates its readiness by sending a dial tone. The calling party then presses the number buttons in a sequence corresponding to the telephone number of the called party.
Then DTMF tones are produced which end up at a
circuit at the exchange. An intermittent ringing signal is sent to alert the called party to an incoming call. If the called party's line is active, the exchange sends a busy signal to the calling party. However, if the called party's line is active but has call waiting installed, the exchange sends an intermittent audible tone to the called party to indicate an incoming call.
AN INTRODUCTION OF BROADBAND TECHNOLOGY
WHAT IS BROADBAND? In telecomm.: In telecomm. it refers to a signalling method
that includes a relatively wide band of frequencies, which may be divided into channels. The wider the bandwidth, the greater the information-carrying capacity. networks or broadband Internet but here data transmission over a fibre optic cable would be referred to as broadband as compared to a telephone modem operating at 56,000 bits per sec.
In data comm.: In data comm. it refers to broadband
TECHNICALLY WE CAN CALL BROADBAND IS A HIGH SPEED INTERNET
SERVICE.
HOW THE BROADBAND WORKS? As broadband is the high speed internet providing
service. It is provided with the help of various equipments to its subscribers. The main components used in providing broadband are 1) DSLAM 2) ADSL 3) MDF 4) SPLITTER 5) ROSSETE
y DSLAM: DSLAM is the abbreviation of DIGITAL SUBSCRIBER LINE ACCESS
MULTIPLEXER.
A DSLAM is a multiplexer located in the telephone company
exchange that provides consumers access to DSL services over twisted pair copper cabling. The device separates the voice and data components from the subscriber lines and aggregates the data for sending over the network.
y ADSL: ADSL i.e. Asymmetric Digital Subscriber Line is one form of data
communications technology that enables faster data transmission over copper telephone lines
ADSL can generally only be distributed over short distances from the
central office, typically less than 4 km.
MDF:y MDF i.e. main distribution frame (MDF) is a distribution
frame on one part of which the external trunk cables entering a facility terminate, and on another part of which the internal user subscriber lines and trunk cabling to any intermediate distribution frames terminate. The MDF is used to cross-connect any outside line with any desired terminal of the multiple cabling or any other outside line.y The MDF usually holds central office protective devices and
functions as a test point between a line and the office.
SPLITTER:An Splitter is a device which is placed along the telephone system in order to separate the voice signals and data signals. By using splitters in the telephone system both the voice and data signals are made available for the users.
ROSSETTE:A Rossette is a device which is used along the phone system in order to remove the noise and interference signals which affects the signal properties. It also takes care of voltage variations in the phone system.
SET UP OF BROADBAND A PICTORIAL PRESENTATIONINTERNET BROADBAND MPS NOS
DIFFERENT TY E OF SERVERS
RE
OTE ACCESS SERVER (RAS) NOIDA
OTHER CITY LOCAL AREA NETWORK (LAN)
OTHER CITY LOCAL AREA NETWORK (LAN)
A
BROAD BANDNETWORK GATEWAY
BROAD BAND NETWORK GATEWAY (BNG) KAN UR
LS NOC, BB-NOC (BANGALORE)
BROAD BAND NETWORK GATEWAY
OTHER CITY LOCAL AREA NETWORK (LAN)
ADIGITAL SUBSRIBER LINE DSLAM DSLAM ACCESS MULTIPLEXER (DSLAM) DSLAM DSLAM
MAIN DISTRIBUTION FRAME (MDF)
DIGITAL SYMMETRIC LINE (CU PAIRS)
SPLITTER
ASYMMETRIC DIGITAL SUBSCRIBER LINE (ADSL)
ROSSETE
PERSONAL COMPUTER
TELEPHONE
AN INTRODUCTION OF GLOBAL SERVICES FOR MOBILE COMMUNICATION (GSM)
GSM NETWORK STRUCTUREOMC
MSC/VLR BSC BIE BTS Abi s BSS C Um MS HLR/ AUC F EIR H SC/VM MSS A MSC/VLR PSTN ISDN PSPDN
E
29
MOBILE STATION ( MS )Equipment used by mobile service subscribers for access to services. Mobile Equipment Subscriber Identity Module (SIM) Mobile stations are not fixed to one subscriber. A subscriber is identified with the SIM card.30
BASE TRANSCEIVER STATION ( BTS )Base Transceiver Station (BTS) Wireless transmission Wireless diversity Wireless channel encryption Conversion between wired and wireless signals
GSM Network Entity
Base Band Unit: voice and data speed adapting and channel coding RF Unit: modulating/demodulating,transmitter and receiver Common Control Unit: BTS operation and maintenance31
BASE STATION CONTROLLER ( BSC )Managing Wireless network-BSS Monitoring BTSCONTROLS:Wireless link distribution between MS and BTS Communication connection and disconnection MS location, handover Voice encoding, transcoding (TC) The operation and maintenance functions of BSS.
GSM Network Entity
32
MOBILE SERVICE SWITCHING CENTER ( MSC )
GSM Network Entity
holds all the switching functions manages the necessary radio resources,
updating the location registration carrying out the inter-BSC and inter-MSC tender
Inter-working with other networks (IWF).
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GSM Network Entity
HOME LOCATION REGISTER ( HLR )Manages the mobile subscribers database
subscriber information part of the mobile location information 3 identities essential the International Mobile subscriber Identity the Mobile station ISDN (Integrated services digital Number) the VLR address
34
VISITOR LOCATION REGISTER ( VLR )GSM Network EntityDYNAMICALLY STORES SUBSCRIBER INFORMATION NEEDED TO HANDLE INCOMING/OUTGOING CALLS
Mobile Station Roaming Number When a roaming mobile enters an MSC area. This MSC warns the associated VLR of this situation; the mobile enters a registration procedure through which it is assigned a mobile subscriber roaming number (MSRN) Temporary Mobile Subscriber Identity, if applicable The location area in which the mobile has been registered Data related to supplementary service parameters
35
AUC/EIRAuthentication Center(s) (AUC)
GSM Network Entity
Providing the authentication key used for authorizing the subscriber access to the associated GSM PLMN. Equipment Identity Register(s) (EIR) Handling Mobile Station Equipment Identity36
FREQUENCY RESOURCEGSM900 :up: 890~915MHz down: 935~960MHz bandwidth: 25MHz frequency interval: 200KHz
EGSM900 :up: 880~890MHz down: 925~935MHz bandwidth: 10MHz frequency interval: 200KHz
GSM 1800 :up: 1710-1785MHz down: 1805-1880MHz bandwidth: 75MHz frequency interval: 200KHz37
GSM 1900MHZ:up:1850~1910MHz down:1930~1990MHz bandwidth: 60MHz frequency interval: 200KHz
