Patent ID: 8189753

Claim:
An intercom system comprising: a hub unit; a plurality of zone units having respective local speakers; the hub unit and zone units interconnected by a cable with four twisted pair wires, with one of the twisted pairs serving as a control bus for sending control messages, and another designated one of the twisted pairs in the same cable serving as an audio bus for distributing, in two directions, intercom system audio signals between at least two of the zone units; wherein the hub unit controls connection of the zone units to the audio bus such that a first zone unit is connected to the audio bus to transmit intercom system audio to be received by multiple ones of the zone units in first direction, and so that a second zone unit is connected to the audio bus to transmit intercom system audio to be received by multiple ones of the zone units in a second direction; and wherein the hub unit also sends a control message to the receiving zone units to couple their respective local speakers to the audio bus, so that only a designated one or more zone units that are an intended receiver of the intercom system audio provide an output that is audible to a user.