BURST FAULT DETECTING CIRCUIT

PURPOSE:To detect a fault of a burst signal by using each of a detection signal of a burst signal and a burst control signal to supervise the state of other signal. CONSTITUTION:A modulation signal outputted according to the burst control signal (c) is fed to an IF circuit, through which an IF signal (a) is outputted and the signal is detected at a detection circuit 23, from which a detected output (b) is obtained. On the other hand, the burst control signal (c) sets the time difference via a delay circuit 24 so as to make the time difference with an output (b) delayed by the circuit 23 proper. Then the output (b) and the signal (c) are inputted to flip-flops 27-30. The flip-flops 27, 28 latch the output (b) at the rise and fall of the signal (c) and the flip-flops 29, 30 latch the signal (c) at the rise/ fall of the output (b) respectively. Then OR circuits 31-33 OR outputs of the flip-flops 27-30 to output a fault alarm (d).