SIGNAL DETECTION DEVICE FOR DISASTER PREVENTION FACILITY

PURPOSE:To prevent wrong alarming and wrong control from being caused by a noise signal by deciding that a received signal is a fire signal, a sent signal such as a control signal, a detection object signal such as a switch input signal, or the noise signal according to whether or not the received signal continues for a specific time. CONSTITUTION:The states of remaining input ports IN2 - IN4 are read in order unless a counter t1 reaches a specific value T1. When the signal state is H every time the state of the input port IN1 is read, namely, when a comparator CM1 receives a signal, the counter t1 counts up by one each time the state is read. Here, when it is judged that the value of the counter t1 reaches the specific value T1, the comparator CM1 receives the signal for a specific time, so it is judged that a correct signal, i.e. the fire signal is detected. Consequently, a microcomputer MPU sets output ports OUT1 and OUT3 to H to turn on a 1st area pilot lamp L1 and displays a fire occurrence area, a main bell MB is driven to indicate the fire occurrence, and an area bell which is not shown in a figure is put in sounding operation while fire prevention doors, etc., are controlled.