To speedily issue a fire alarm from both an emergency fire transmitter and a fire sensor even in case of power supply stop by providing a repeater with a power supply stop detecting means for outputting a storage cancel signal to a transmitter responding terminal when power supply is stopped.
A repeater 1 is provided with a voltage discrimination circuit 11 for always monitoring the voltage level of sensor line L and discriminating the alarm due to a fire sensor S and the alarm due to an emergency fire transmitter P and a switching circuit 12 for short-circuitting and connecting a transmitter response line LA to a common terminal C. A power supply stop detecting means B is constituted by combining these voltage discrimination circuit 11 and switching circuit 12. When power supply to the repeater 1 is stopped, the storage cancel signal is transmitted to a fire receiver 2 and storage operation is canceled so that the alarm from the fire sensor S and the emergency fire transmitter P can be speedily issued.
NAKAGAWA YOSHIAKI