A telephone system for providing communications between mobile radiotelephones, portable radiotelephones and landline telephones includes a land-line telephone system including a land-line switching network for providing communication paths for land-line telephones and a mobile radiotelephone system for providing communications paths for mobile and portable radiotelephones. The mobile radiotelephone system includes a digital switching network, base stations, and PCM analog-to-digital (A/D) and digital-to-analog (D/A) converters interposed between the base stations and the digital switching network and between the land-line switching network and the digital switching network. Analog ports are interfaced by the PCM A/D and D/A converters to incoming and outgoing serial bit streams coded according to pulse-code-modulation (PCM) techniques standardized for telecommunications systems by the International Telegraph and Telephone Consultative Committee (CCITT).
The digital switching network receives the incoming serial PCM bit streams and provides the outgoing serial PCM bit streams so that telephone calls are automatically routed between the calling and called parties in the telephone system. Supervisory signalling is detected from the incoming serial PCM bit streams and processed by a signal processing computer to determine an ordering of time slots for the PCM channels for controlling the interchange of PCM channels from the incoming serial PCM bit streams to the outgoing serial PCM bit streams. Supervisory signalling for outgoing PCM channels corresponding to the incoming supervisory signalling from incoming PCM channels is adapted to to a pre-established format recognized by the corresponding outgoing PCM channels and multiplexed into the respective outgoing serial PCM bit streams.