Sensor monitoring alarm system

摘要

A time multiplexed sensor monitoring system. A plurality of remote sensor units are connected to a central control unit by a two-wire bus line. Power is supplied to the remote unit sensors by the central control unit. Synchronization of the remote units is provided through momentary interruptions in the power supplied to the remote sensor units. The use of a single two-wire bus line for both application of DC signals to the respective remote sensor units and communication of data from the remote sensor units to the central control unit is facilitated by use of double tone multi-frequency (DTMF) signalling techniques.