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WIRED WIRED COMMUNICATIONCOMMUNICATION

SWITCHING AND TRANSMISSION IN LANDLINE PHONES AT

INSTITUTE OF ENGINEERING AND TECHNOLOGY, ALWAR

2011-2012 BY:- POORNIMA SHARMA VIPIN TIWARI EC- B

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CONTENTS:-1. Heading2. content3. Switching4. Main units of switch room5. CSN6. SMC7. SMA AND SMT8. SMX9. SMM10.OPTICAL FIBRE TRAMSMISSION11.TRANSMITTER AND RECEIVER12.SPLICING TECHNIQUE13.MDF14.REQUIREMENT OF MDF15.N.E NUMBER ASSIGNING16.TRANSMISSION BETWEEN EXCHANGES17.SEQUENCE OF TRANSMOSSION18.END

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SWITCHING

Switch:• Control consisting of a mechanical or electrical or electronic device for making or breaking or changing the connections in a circuit.And the process is called SWITCHING.

• Following are various types of switches.

DEFINITION:-

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Switching techniques

• Usually circuit switching is used worldwide for land line communication.

• Dedicated communication path between two stations.

• Three main phases:-1. Establish2. Transfer3. Disconnect

• Must have switching capacity and channel capacity to establish connection.

• Must have intelligence to work out routing

CIRCUIT SWITCHING:-

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MAIN UNITS OF SWITCH ROOM

•Switch room in a telephone exchange consists of various units for call processing which are as follows:-

1. CSN:-• There are basically two types of CSN in any telephone exchange.• These two CSN’s are namely CSN base and CSN extension.• The difference between these two is that CSN base consists of two logic

circuits namely logic 1 and logic 0.• There are 4 shelves in every CSN. Each shelf consists of 2 modules

which consist of 8 subscriber card.• Since there are 7 modules thus each module can provide service to 128

subscribers.

(SUBSCRIBER CARD)>>>

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• Every subscriber card can connect 16 subscribers.• Each CSN base can have 4 extensions not more than that.• Thus one local exchange can have many bases.• The most basic function of CSN is that it is the first interface of the analog voice signal.• It keeps on checking the procedure of an call and working of other units of switch room.• The subscriber cards in CSN are for the sampling of analog voice signal.

(CSN base) (subscriber card)

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(2) SMC (Main Control Station) :-• When ever discontinuation of dial tone need to be done then this unit comes into action.

• SMC provides input to another unit of exchange namely SMX (Main Switching Station).

• SMC is responsible for storing all the information of metering (billing) of every call which is made and under process.

• It keeps in connection with the CSN as it keeps the track of all the calls.

• Main parts of smc 1. TX (charging unit) 2. MR (multi register) 3. TR (translator)

(SMC)>>>

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3. MAIN TRUNK STATION (SMT):-

• SMT is used for the trunk (STD) calls.

• If the dialled number is of same area then CSN handles that, but if it goes out of state or out of any particular assigned area then SMT controls.

• SMT is connected through token rings with other units.

4. MAIN AUXILLARY STATION (SMA):-

• After the CSN acknowledges that a call is to be made then SMA provides the dial tone to the subscriber.

It has different cards which are just electronic circuits.

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5. MAIN SWITCHING STATION(SMX):-

• SMX is the main switching or the host switching unit.• It provides 32 channels through every PCM out of which only 30 are provided and rest 2 are reserved for syncronization and testing purpose.

• SMX is a very compulsory unit, when the digits are dialled by a subscriber then SMX detects whether the call is from the same CSN or other exchange or STD.

• If it is a STD call then SMX informs SMT for further processing.

• And if call is through same CSN then it informs the CSN.

• The first 4 digits of any phone no. are used to determine whether the call is STD ISD or local. This action is done in SMX only.

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6. MAIN MONITORING STATION (SMM):-

• SMM is used to dispatch the bills of every subscriber of that exchange and keeps monthly record.

• It takes the input from SMC which keeps the daily account and keep sending to SMM.

• It consist of magnetic tape which stores the monthly billing information.

• This tape is analyzed every 15th or last day of every month.

(SMM) (MAGNETIC TAPES)

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FiberDriver Source Detector Regen.

Transmitter Receiver

Transmission through OPTICAL FIBER

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•Transmitter convert electrical signal to optical signals which is transmitted through fibre •Electronic interfaces•Electronic processing circuits•Drive circuitry•Light source – LED/Laser•Optical interface•Output sensing and stabilization•Temperature sensing and control

BASIC ELEMENTS FOR TRANSMISION AND RECEIVE

TRANSMISION

•Receiver- receives the optical signals from the fibre and convert the same to its electrical equivalent•Detector [APD (Avalanche photodiode]•Detector used are semiconductor photodiodes or photo-detectors which converts the received optical signal into electrical form •Amplifier•Decision circuits

RECEIVER

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SPLICING OR CONNECTING TWO FIBERS

It involves permanent connection b/t two fibers including cutting edges of two fibers to be spliced, their allignement of cores and reducing losses.

Fusion splicing>>>>>

Mechanical splicing>>>

(PRN 600)

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INTRODUCTIONTo obtain the flexibility in interconnecting external line plants and the exchange equipments and between different circuits in the exchange itself, certain arrangement is made by the use of iron frames. These iron frames are called Main Distribution Frames (MDF), or Intermediate Distribution Frames (IDF) or some times Combined Main and Intermediate Distribution Frames (MIDF), depending upon their functions.

MDF (MAIN DISTRIBUTION FRAME)

(N E side)>>>>>

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MAIN DISTRIBUTION FRAMES (MDF) – Why MDF is required in exchanges?

All lines within the exchange are in strict numerical order, whereas subs lines coming from different areas in any cable they are haphazard i.e. not in a numerical sequence.When a telephone is disconnected or transferred to another area, the exchange numbering on any external cable pair also constantly changes.It is therefore necessary that some means must be provided for temporary connection between the two.This conversion from the geographical orders of the external pairs to the numerical order within the exchange is carried out on MAIN DISTRIBUTION FRAMES.

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N E no. or equipment number assigning

•Through the switch room every subscriber is given a unique equipement number called N E no.

•After allaoting the n e no. connection is made at MDF room.

•MDF room has different tag blocks each having a capacity of 128 pairs.

The connection made is in following form:- •Switch room >> n e side of MDF >> jumper wires >> line side of MDF and then it finally goes to the subscriber side.

•Reverse order of this is followed while traveling from subscriber end to the switch room.

•eg, of n e no. > 21 – 6 – 3 . (TAG BLOCK)

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Transmission between the telephone exchanges

• As there are different exchanges for different areas , each having a approximate area of 5 kms., so they needed to be connected to connect other areas.• Now a days all the connections between the exchanges is done through Optical fibers only.• The room which is made for this purpose is called optical fiber transmission room (OFT ROOM).• This room has following parts for the transmission. 1. STM2. PCM CABELS3. TIRE 1, TIRE 2 SWITCHES4. OPTICAL FIBER CONNECTORS5. PCM CABEL JUNCTIONS6. PROPER AIR CONDITIONING.

(Pcm cable connector)>>

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Sequence followed for transmission in exchanges

•In OFT room transmission between exchanges is carried out, this transmission is through optical wire.

•First of all, the sampled signal from switch room comes to the pcm cable connectors. This signal comes through PCM cables.

•This signal is then transferred to digital signal transmitters (DST).

>> >>

(switch room) (pcm cable connector) (DST)

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•Then after DST the signal goes to the STM .

•STM Is a very important part of optical fiber trasmission room.

•At stm the digital signal is converted into light signal which can be transmitted through the optical fiber cable.

•This stm has laser diodes and photo diodes which work as accordingly.

•There are two rings of optical fibers between the exchanges. So that if one goes failure then other can work.

>> >> OTHER EXCHANGE

(STM) (FIBER)

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END

THANKS A TON