| 摘要 |
PURPOSE:To constitute a fire alarm system without increasing considerably the number of repeaters, even if the fire alarm system becomes large in scale and the number of circuits increases, by utilizing effectively to the maximum a control data of the excessive number of bits set in advance and the return signal. CONSTITUTION:When one of fire sensors 3 connected to a circuit l1 senses a fire and the circuit l1 is short-circuited, a large current flows through a resistance R1 and a switching transistor Tr1, in an input/output circuit 2b1, a light emitting diode provided on the input side of a photocoupler PH4 is made to emit light by a voltage across the resistance R1, the 5-th terminal of an IC1 is set to an L level, and a fire warning signal is inputted to the IC1. As a result, the IC1 sets the second bit of a return signal RP to an H level, and transmits information of the occurrence of a fire to a receiver 1. The receiver 1 decides each bit of the return signal RP, and if the bit corresponding to the information of the occurrence of a fire is at an H level, it is decided that the fire sensor 3 of a prescribed, for instance, the circuit l1 connected to a repeater of an address has raised a fire alarm signal, and a fire alarm is raised.
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