03-Tw2103eu01 Eg0001 Digital Transmission Systems

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Digital Transmission Systems Siemens

3 Digital Transmission Systems

Contents Pages

1 Digital Transmission Systems 12 Objectives 23 Transmission Systems PCM30 34 Pulse Frame! Frame "lignment Signal #F"S$ %

Service &or' %% Digital Transmission Systems o( )ig*er Ca+acity ,, PCM -in.s bet/een c*anges

Summary 11

T*e transmission systems PCM 30 an' PCM 24 combine 30 an' 24 c*annelsres+ectively to (orm a time multi+le system T*ese systems are recommen'e' byCC TT

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Siemens Digital Transmission Systems

3.1 Objectives

5+on com+letion o( t*is c*a+ter8 you /ill .no/ t*e basic 'esign o( PCMtransmission systems8 es+ecially o( t*e transmission system PCM 30

9ou /ill be able to

+lain t*e 'esign o( PCM 30 +ulse (rame +lain t*e term digital transmission of higher capacity

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3.2 Transmission System PCM 30

n a PCM transmission system8 se+arate c*annels are +rovi'e' (or eac* 'irection o(s+eec* One +air o( /ires is re:uire' (or each 'irection o( transmission

Fig. 1

Design of a PCM Transmission System 1

PCM transmission systems terminate at bot* en's in a digital multiplex unit ac*multi+le unit *as a transmitter section an' a receiver section T*e transmittersections create t*e , bit PCM binary co'es to be transmitte'8 an' t*e receiversections convert t*e receive' PCM binary co'es bac. to analog signals

Fig. 2

T*e bloc. 'igram -F;PCM stan's (or t*e conversion o( a lo/ (re:uency analog signal into a 'igitalPCM signal an' vice versa T*ere(ore8 it corres+on's to t*e bloc. 'iagram (or analog;'igitalconversion

Regenerative repeaters are installe' on PCM transmission routes at intervals o(

roug*ly 2 to ! .mT*ey regenerate t*e PCM signals in bot* 'irections8 t*us eliminating any 'istortion

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"t t*e en' o( t*e transmission lin. < irres+ective o( its lengt* an' :uality < a signal/*ic* is almost inter(erence7(ree is available

Fig. 3

T*e line terminating unit is t*e lin. bet/een t*e 'igital multi+le unit an' t*etransmission linest +rovi'es t*e (ee'ing current (or t*e regenerative re+eaters an' regenerates t*ePCM signal on t*e receiver si'e

Fig. 4

T*e transmission system PCM 30 allo/s t*e simultaneous transmission o( 30 callsinclu'ing signaling an' sync*roni=ing

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One +air o( /ires is re:uire' +er call 'irection

Fig. 5

ac* call nee's a time slot in 'irection " 77 > an' a time slot in 'irection > 77 "ncoming an' outgoing calls always use t*e same time slot number

Time slots /*ic* belong toget*er are calle' a trun.

Fig. 6

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3.2.1 Pulse rame " PCM 30 +ulse (rame consists o( 32 time slots #c*annels$

Fig. 7

Time slots 1 to 1! an' 1% to 31 are use' (or transmitting calls n time slot 08 t*eframe alignment signal an' t*e service word are transmitte' alternatelyTime slot 1 can be use' as signaling c*annel or as a''itional s+eec* c*annel #seeC"S;CCS$

T*e +ulse (rames are transmitte' in a consecutive or'er

Fig. 8

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3.2.2 rame !lignment Signal

T*e (rame signal is use' (or t*e sync*roni=ing o( t*e transmitter;receiver o( a PCM30 transmission lin. T*ey al/ays *ave t*e same bit +attern

Fig. 9

3.2.3 Service "or#T*e service /or' transmits service signals For e am+le8 bit 3 is set in case o( urgentalarm

Fig. 10

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3.3 Digital Transmission Systems of $ig%er Ca&acity

Digital transmission systems /it* a *ig*er number o( c*annels are base' on t*esystems PCM 30 an' PCM 24

Fig. 11

Coa ial cables or o+tical (ibers are use' as transmission lin.sn t*e 'igital signal multi+le unit8 t*e 32 c*annels o( a PCM system are /ritten into acyclic memory 4 c*annels are store' +er /rite7in cloc. #(?2M)=$ T*e rea'7out cloc.(or t*e cyclic memory is (?,M*= T*e 4 32 c*annels combine' in t*is /ay areassigne' a (rame signal #F"S$

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3.' PCM (in)s bet*een +,c%anges

"nalog e c*anges # @C)$ can be connecte' to a PCM system /it* multi+le units

T*e e c*anges are 'irectly lin.e' to t*e PCM system via t*eir analog out+uts #only27/ire in t*e e am+le$

Fig. 12

"t t*e outlet o( a 'igital e c*ange8 t*e tele+*one signals are alrea'y available asPCM signals #PCM 30 or PCM 24 (ormat$ T*ere is no multi+le unit re:uire' on t*issi'e o( t*e PCM transmission system

Fig. 13

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&*en t*ere are PCM lin.s bet/een t/o 'igital e c*anges8 t*ere are no multi+leunits on eit*er si'e

Fig. 14

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3.- Summary

Digital Transmission Systems

PCM transmission systems are 47/ire systems

T*ere are t/o basic PCM systemsA PCM 30 an' PCM 24

t is +ossible to generate 'igital transmission systems o( *ig*er ca+acity base'

on t*ese t/o systems

Per PCM 30 +ulse (rame8 sync*roni=ation or alarm in(ormation is transmitte'

alternately in time slot "

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03-Tw2103eu01 Eg0001 Digital Transmission Systems

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