Communications repeater monitoring system

Abstract

A monitoring and alarm system for a radio frequency microwave communications repeater unit. A plurality of signals representative of the status of a corresponding plurality of operating conditions of the repeater unit are simultaneously generated. The signals are time multiplexed to form a combined signal. The combined signal is encoded to form a digital signal of frames of data having a frequency substantially less than the communication signal carrier frequency and preferably less than the communication modulating signal frequency, with a frame being formed of data from each of the status signals. A variable attenuator is responsive to the digital signal for varying the level of the communication signal proportionally with the value of the digital signal. The level-varied communication signal is then retransmitted. At a receiver unit for receiving the retransmitted communication signal there is an automatic gain control circuit responsive to the signal level of the received retransmitted communication signal for generating a control signal indicative of the level of the received communication signal. The digital signal is regenerated from this control signal and is decoded into a plurality of output signals corresponding to and representative of the original operating-condition-status signals.