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(, , ). , (bearer service) (, speech, unrestricted 3.1 kHz audio) (. Group. 4 Fax, Teletex, Videotex), . (low layer compatibility) , .
. , SETUP (bearer service), INFORMATION. , SPEECH SETUP , , INFORMATION .
CALL PROCEEDING , .
SETUP . , NT , SETUP . (bearer capability) (, . 4, ). (. 4) ( TEI =4 8) ALERTING . (, ). , (, ), CONNECT . , CONNECT, - CONNECT ASKnowledge, - . , , RELEASE, , . CONNECT , CONNECT , . .
. : Disconnect, RELease, RELease COMPlete.
, D - , ISUP, , , , , ISDN .
ISDN.
ISDN- :
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;
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INTERNET;
(, );
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25.