RECEIVER MONITORING SYSTEM

PURPOSE:To simplify circuit constitution by allowing the common receiver of a center station to receive monitor pilot signals of different frequencies sent out of plural terminal stations, and deciding that the common receiver is faulty when the detection output drops below the detection level of one wave. CONSTITUTION:Respective terminal stations #1-#n of a multidirectional SSB communication system convert monitor pilot signals PL of allotted frequencies fP-1-fP-n to determined frequencies in a preset monitor signal transmission common band S. The center station #0 receives transmit signals D-1-D-n and monitor signals PL from the respective terminal stations by the common receiver 40, and they are demodulated and outputted to a terminal 30. A demodulated signal PL is extracted by a BPF41 of the band S, detected 42, and inputted to a decision circuit 31. The circuit 31 decides that the receiver 40 is faulty when the mean composition level of detection signals is lower than the detection level of a monitor signal PL corresponding to one wave, and outputs fault monitor information from a terminal 32.