| 摘要 |
PURPOSE:To improve the reliability of a monitor at the maintenance by checking the entire gain of a receiver and monitoring the deterioration in a main signal input to the receiver with an output resulting from ANDing the detection signal of the main signal. CONSTITUTION:A detector 12 for a pilot signal detects a pilot signal component in an intermediate frequency f3 in an output of an AGC amplifier 8, its detected output J is sent to a comparator circuit 14, in which an output N of a pilot signal oscillator 20 and a detection voltage K detected by a detector 13 are compared to detect a difference from the voltage K representing the entire gain of a predetermined receiver. After the presence of the deterioration in the entire gain of the receiver is checked by using a detection signal P, an output H of the detector 11 and a main signal are ANDed at an AND gate 15 to obtain a monitor output. When the absence of the deterioration in the entire gain of the receiver is confirmed by the detection signal P of the comparator 14 and the detected output H of the main signal is lower than the standard value, it is discriminated that the reception input of the main signal to the receiver is decreased. Thus, a fault of the receiver is monitored by distinguishing it from the decreased reception input level of the main signal. |
