Abstract: A transmission system comprises apparatus for the transmission of voice signals only, data signals only, or a combination of both voice and data signals in a multiplexed stream of eight bit time slots over a single, bidirectional digital channel for a point-to-point connection. In the combined mode, the encoded voice signals, using low bit rate voice encoders, are assigned to four bit positions of the eight bit time slot; the data signals are assigned to the remaining four bits. Up to two bit positions normally used for data may be used for signature bits, thereby identifying whether the multiplexed stream comprises voice signals only, data signals only, or a combination of both voice and data signals. Also, a minimum of one "1" bit per eight bit time slot is thereby guaranteed.