Abstract: Multiplexing and demultiplexing equipments are provided for in end stations of a bidirectional synchronous digital link in which one of the multiplexed signals offers a variable rate at the request of either of the stations. The resultant signal transmitted on the link has a variable modulation speed as a function of the rate requested. More particularly, in an integrated services digital network, a multiplexing equipment and a demultiplexing equipment are intended to provide a non-specific interface for a subscriber monitoring system or terminal connected to the system so that each interface can dynamically define the rates used in both directions of transmission. This allows connections of any terminal, whatever the rates it requires in both directions of transmission, to any of terminal ports of the system, which are also non-specific.

Abstract: A telephone simulator includes a plurality of pseudo subscriber circuits connected to subscriber lines. A plurality of pseudo junctors are connected to trunk lines. A number of detector circuits respond to line conditions, tones, circuit operations, data processing, and the like. A data processor uses these equipments to check incoming and outgoing calls to and from a public telephone network.