Fire alarm system, fire sensor, fire receiver, and repeater

摘要

Disclosed herein is a fire alarm system for connecting a plurality of fire sensors (13) to sensor lines (12a to 12d), and giving an alarm in response to fire information output from the fire sensor (13) in a line unit. The fire alarm system includes a current modulation section (47, 48, 49) and an address specification section (22, 23, 24, 27_1 to 27_n). The current modulation section is used for maintaining a current flowing in the sensor line at a predetermined value for a predetermined time at the time of a fire, andmodulating the current in accordance with the inherent address information of the fire sensor. The address specification section is used for sensing fire information by judging whether or not the current has been maintained at the predetermined value for the predetermined time, and also for specifying the inherent address of the fire sensor that issued the fire information, from the modulated state of the current.