04-tw2103eu01 eg0001 digital switching

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Digital Switching Siemens

4 Digital Switching

Contents Pages

1 Digital Switching 12 Objectives 23 Switching Principles 34 Space Switch 35 Time Switch 56 Space-Time Switch 67 !"ipment in a Digital #change $$ Terminating !"ipment %% Digital Switching &etw'r(s 1)1) *'nnecti'n between Tw' S"bscribers 1111 S"mmar+ 12

The ma#im"m transmissi'n !"alit+ ,'r teleph'ne signals is achieve i, e#cl"sivel+igital signals are transmitte al'ng the highwa+s. incl" ing the e#changes/

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Siemens Digital Switching

4.1 Objectives

p'n c'mpleti'n ', this chapter. +'" will (n'w the principle ', switching 'perati'nsin igital switching netw'r(s/

'" will be able t'

#plain the ,"ncti'ning ', time switch. space switch an space-time switch #plain the main tas(s ', a igital e#change

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4.2 Switching Principles

Digital e#changes establish c'nnecti'ns b+ rearranging the $ bit binar+ c' es ',vari'"s teleph'ne signals as speci,ie b+ the call re!"est/

Fig. 1

4.2.1 Space Switch

The space switch can switch an+ $ bit P* binar+ c' e ,r'm the inc'ming highwa+st' an+ '"tg'ing highwa+ without change ', time sl't/

Fig. 2

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The thr'"gh-c'nnecti'n is per,'rme b+ means ', electr'nic switches &D gate /The e#act se!"ence in which the AND gates are t' be t"rne O& 'r O88. isin icate in the control memory / 8'r each time sl't t1 9 t3 . the &D gates is

switche again/

Fig. 3

Fig. 4

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4.2.2 Time Switch

The time switch can switch an+ $ bit P* binar+ c' e ,r'm the inc'ming highwa+ t'

an+ time sl't 'n the '"tg'ing highwa+ ,"ll availabilit+ / 8'r this. the inc'ming binar+

c' es are written int' the data memory c+clicall+/

Fig. 5

s speci,ie b+ the call re!"est st're in the c'ntr'l mem'r+. the c' e w'r s are

rea '"t again/

Fig. 6

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sec'n meth' is t' s'rt an st're the binar+ c' es as speci,ie b+ the call

re!"est/

The+ will be rea '"t c+clicall+/

Fig.7

4.2.3 Space-time Switch

The Space-time switch is a high-spee variati'n ', the time switch/ :eca"se ', its

high 'perating spee . it can switch an $ bit P* binar+ c' e ,r'm several inc'ming

highwa+s t' an+ time sl't ', several '"tg'ing highwa+s/ T' achieve this. P* binar+

c' es ', the inc'ming highwa+s m"st be c'mbine m"ltiple#e an e#ten e t' the

ata mem'r+/ This means that the highwa+ ,r'm the m"ltiple#er t' the ata mem'r+

has a bit rate which is several times higher than that ', the inc'ming highwa+/

;n the e#ample sh'wn. the highwa+ ,r'm the m"ltiple#er t' the ata mem'r+ has a bit

rate which is ,'"r times as high as the bit rate ', a single inc'ming highwa+/

8'll'wing the switching. the em"ltiple#er istrib"tes the P* binar+ c' es t' ,'"r

'"tg'ing highwa+s 'perating at the 'riginal bit rate/

;n all 'ther respects. the space-time switch w'r(s 'n the same principles as the timeswitch/ ;t als' enables that an+ P* binar+ c' es 'n the inc'ming si e is switche

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t' an+ time sl't 'n an+ ', the ,'"r '"tg'ing highwa+s with'"t bl'c(ing ,"llavailabilit+ /

Fig. 8

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4.3 !"ipment in a #igital $change

Digital e#changes have tw' main ,"ncti'nal areasing igital signals

$ ' ing anal'g ? igital c'nversi'n

) +bir 2-wire ? 4-wire c'nversi'n

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* est ccess e/g/ testing ', s"bscriber line

4.3.2 Digital Switching %etwor&

Digital switching netw'r(s c'mprise the time. space-time an space switches

escribe in previ'"s chapters/

These switches can be "se in ivi "all+ 'r in an+ esire c'mbinati'n/ c'mm'n

c'mbinati'n is the time ?space?time c'n,ig"rati'n/ The c'mbinati'n act"all+ "se

epen s 'n the switching s+stem c'ncept an the si>e ', the e#change/

Fig. 11

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4.3.3 connection between Two S"bscribers

O"r e#ample sh'ws a c'nnecti'n between s"bscribers an :/ The $ bit binar+

c' es ,r'm s"bscriber line are sent t' the switching netw'r( in a time sl't 'n

highwa+ 1/ The+ are switche t' a partic"lar time sl't 'n highwa+ n an sent t' the

terminating e!"ipment ', s"bscriber line :/

The binar+ c' es ,r'm s"bscriber : are sent via highwa+ n. the switching netw'r(

an highwa+ 1 t' the terminating e!"ipment ', s"bscriber line / ,'r the "rati'n ',

the c'nversati'n between s"bscriber an :. these tw' paths are m'mentaril+

c'nnecte thr'"gh 'nce ever+ 125 s peri' /

s s''n as the c'nversati'n is 'ver. the tw' paths thr'"gh the switching netw'r( will

be release @ the relevant c'ntents ', the c'ntr'l mem'r+ will be erase / The timesl'ts which have been release can n'w be "se again ,'r 'ther c'nnecti'ns/

Fig. 12

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4.4 S"mmar'

Digital Switching

0ith c'nnecti'ns via time switch. the binar+ c' es change their m"ltiple#

highwa+/

Digital switching netw'r(s c'nsist ', a c'mbinati'n ', time an space

switches/

Thr'"gh-c'nnecti'ns in igital switching netw'r(s alwa+s c'rresp'n t' 4-wire

thr'"gh-c'nnecti'ns in anal'g netw'r(s/

The i,,erent tr"n( lines m"st be a j"ste ,'r the thr'"gh-c'nnecti'n via the

switching netw'r(/

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04-tw2103eu01 eg0001 digital switching

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