Multiple line telephone instrument

摘要

The present invention is directed to a multiple line telephone instrument operative over a pair of data conductors and a pair of speech conductors using time division principles. The data pair transmits line condition signaling and control using an asynchronous sixteen bit binary code while the speech and dialing information is sent over the speech pair of conductors in standard analog format for translation to PCM code within the system (not shown herein). Line condition signaling between an instrument and its group logic circuit or group processor is in parallel over the data pair. Incoming line condition signaling information is used to generate an audible signal and to illuminate a selected lamp representing the desired line. Outgoing line condition signaling is encoded in diphase code using a square wave of a second frequency to represent a binary zero. The outgoing encoding ensures that only one or the other binary signal is sent and to ensure that the signals are sent in diphase mode.