ALARM DETECTING CIRCUIT

PURPOSE:To produce an alarm for only a failure of a low-order group device system without producing an alarm for a failure of a high-order group device system, by storing an AIS signal in a storage device. CONSTITUTION:When the AIS signal is transmitted at the failure of the high- order group device system, this signal is detected by an AIS detection circuit 9 and a signal of ''1'' level is outputted. A synchronism failure and input interruption detecting circuit 8 detects out-of-synchronism or interruption of input signal, and a signal of level ''1'' is outputted. A storage device 12 is set at a rising part (0 level to 1 level) of a signal from the circuit 9, the output of the circuit 8 is inhibited at an AND gate 13, and no alarm output produces in case of the failure of the high-order group device system.