a multiplexer / demultiplexer system for multiplexing and demultiplexing information from a plurality of traffic channels is configured according to a plesiochronous digital hierarchy standard into a composite signal transferred to and from a telecommunciations interface . a pdh traffic interface receives pdh channel signals from a plurality of pdh channels and a bit - pipe interface receives bit - pipe traffic transported as a packet data stream . a composite signal generation module and interface then creates , outputs and receives a single composite serial data stream including , in a single composite format , information from the received pdh channel signals as well as the packet data stream . the rate of the bit - pipe traffic may be adaptively modulated as a function of the composite rate .