Abstract: A PCM telephone switch that is simultaneously compatible with both DS-1 and CEPT PCM formats is disclosed. A switch module performs timeslot switching of individual subchannels between DS-1 and CEPT trunks which are input by way of digital group interfaces. Each group interface couples to one or more trunks of serial bit streams of either DS-1 or CEPT format standards. After the input serial bit stream is converted to a parallel format, it is used as eight bits of the address bits of data processing ROMs from which a corresponding 8-bit word is parallel read on a per channel basis and routed to the appropriate output data processing ROMs. The output data bits of the ROMs are the processed data bits which are reconverted to serial format for either DS-1 or CEPT standards as required by the output trunk. A-law or .mu.-law decoding and encoding is accomplished independently from input to output channel on a per channel basis.

Abstract: A digital radiotelephone exchange having self diagnostic individual subchannel loopback is disclosed. An individual subchannel of an outbound PCM data stream is substituted for an individual subchannel of an inbound PCM data stream. The removed individual subchannel of the inbound PCM data stream is either substituted in the outbound PCM data stream or discarded. Line signal bits may be generated and substituted for the line signal bits of the individual subchannel in the outbound PCM data stream.

Abstract: A three-party conference circuit provides for three-party conference calls in time-division-multiplex communication systems utilizing pulse-code modulation. The digitized speech signals from a selected group of channels are received from an incoming PCM highway, expanded from PCM coding to linear coding and consecutively stored in groups of three in three registers. Different pairs of the registers are selected by a multiplexer, after which the speech signals from the selected pairs of registers are added to provide a combined speech signal. The combined speech signals are compressed from linear coding to PCM coding and applied to an outgoing PCM highway for transmission to the respective parties. Since the speech signals are combined and retransmitted essentially within the same frame, time delay distortion of the audio signals is minimized.

Abstract: 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).

Abstract: A three-party conference circuit provides for three-party conference calls in time-division-multiplex communication systems utilizing pulse-code modulation. The digitized speech signals from a selected group of channels are received from an incoming PCM highway, expanded from PCM coding to linear coding and consecutively stored in groups of three in three registers. Different pairs of the registers are selected by a multiplexer, after which the speech signals from the selected pairs of registers are added to provide a combined speech signal. The combined speech signals are compressed from linear coding to PCM coding and applied to an outgoing PCM highway for transmission to the respective parties. Since the speech signals are combined and retransmitted essentially within the same frame, time delay distortion of the audio signals is minimized.