AUTOMATIC FIRE ALARM SYSTEM

摘要

PROBLEM TO BE SOLVED: To guarantee polling performance through a backup trunk line at a maximum when abnormality of communication such as a disconnection or short circuit occurs to a transmission trunk line in use as an ordinary operating trunk line and a trunk line backup process is performed. SOLUTION: A fire receiver 1 sends a trunk line temporary switching signal periodically to a repeater 2, which receives this trunk line temporary switching signal and performs trunk line switching operation to electrically connect to the other transmission trunk line L2. Then the fire receiver 1 performs trunk line switching operation when the repeater 2 electrically connects to the other transmission trunk line L2 to electrically connect to the other transmission trunk line L2 and confirms the communication state of the other transmission trunk line L2 by polling with the repeater 2 through the other transmission trunk line L2.