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Chapter 8

Circuit Switching & Telephone Network

1. Circuit switching

2. Telephone network

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Switching

Whenever we have multiple devices, we have the

prolem o! how to connect them to make one"one"

one communication possile.

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Circuit"switched Network

# Creates a direct ph$sical connection etween two devices

such as phones or computer

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% Circuit Switch

# evice with n inputs and m outputs that creates atemporar$ connection etween an input link and outputlink

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% 'olded Switch

# n"$"n !olded switch can connect n lines in !ull"duple(

mode

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Circuit Switching Technologies

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Crossar Switch

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Crossar Switches) *rolem

# The numer o! switches is huge.

+ connect n inputs $ m output "" reuire n - m

crosspoint.

+ ( ) 1/// input, 1/// output 0 1,///,/// crosspoint

# ne!!icient

+ !ewer than 23 o! the crosspoints are in use at a given

time.

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4ultistage Switch

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Switching *ath

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4ultistage Switches) %dvantage

# %dvantage) The numer o! crosspoints+ single"stage switch

5 need 22 crosspoint61 - 17

+ multistage switch

5 !irst"stage ) 1/ crosspoint6 - 27 - 9 / crosspoint

5 second"stage ) : crosspoint6 -7 - 2 9 18 crosspoint

5 third"stage ) 1/ crosspoint6 - 27 - 9 / crosspoint

total numer o! crosspoint ) ;8

# isadvantage) Call locking

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T4, with and without TS

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Time"Slot nterchange

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T4

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Cominations

# Space ivision SW ) Simple 6=7, Crosspoints 6>7

# Time ivision SW ) *rocessing dela$ 6>7

# Space"and Time"ivision Switching cominations

take advantage o! the est o! oth

+ TST6time"space"time7

+ TSST6time"space"space"time7

+ STTS6space"time"time"space7

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TST Switch

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% Telephone S$stem

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Telephone Companies)

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A%T%s

# % A%T% can e a small or large metropolitan area

# ntra"A%T% services are provided $ local

e(change carriers

+ AC 6ncument Aocal (change Carriers7

+ CAC 6Competitive Aocal (change Carriers7

# nter"A%T% services are handled $ >Cs 6nter"

(change Carriers7+ Called long"diatance companies

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Switching =!!ices in a A%T%

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*=* 6*oint o! *resence7

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Botar$ and Touch"Tone ialing