Importance

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Abstract

A system for interfacing a plurality of analog telephones to an integrated services digital network (ISDN) line of telecommunications network is disclosed. The system comprises a plurality of line interface units connected to respective telephones and a distribution line, and a communications controller interconnects the distribution line and the ISDN line. The communications controller transmits digital data frames on the distribution line, each frame having a frame start and a plurality of control channels and voice channels of which respective voice and control channels are associated with respective line interface units. The controller can instruct each line interface unit on the control channel of that unit, to issue ringing voltage, dial tone, busy tone or ringing tone, and it selectively couples the voice channels to the ISDN line. Each line interface unit can inform the communications controller, on the control channel of that unit, of switch-hook status of the connected telephone, a dialed directory number or dual tone multi-frequency (DTMF) digits collected. It also performs analog to digital coding and decoding of outbound and inbound voice signals, respectively, between the connected telephone and the voice channel of that unit.

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First Claim