| 摘要 |
A circuit for the subscriber termination in an integrated services digital network (ISDN) to which a number of individual terminals are connected by respective S-interfaces, or by S-interface busses respectively combining a number of terminals into a common ISDN network termination, each subscriber line having a B+B+D channel structure, has a switching matrix operated by a switching control for selectively connecting B-channels to each other or through-connecting a B-channel to a switching center. The D-channels in the transmission direction toward the switching control are supplied to an AND gate having an output which is a common D-channel connected to the switching control and which is also connected through a common D-echo channel to the D-echo channels in the opposite transmission direction associated with the S-interfaces. The D-channels in the transmission direction toward the switching control are also connected to an identifier which supplies information to the switching control identifying from which S-interface the signal being transmitted arises.
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