| 摘要 |
PROBLEM TO BE SOLVED: To easily find the number of fire alarms connected to a receiving part. SOLUTION: Each fire alarm 4 shows prescribed resistance value only when a common terminal and a line terminal are made to reverse power supply and a receiving part 12 discriminates the number of connected fire alarms 4 from current value to be obtained when the power supply of a common line 2 and a line wire 3 is reversed. The, when the number of connected fire alarms is preliminarily known, a connection state can be confirmed to be normal and also when the inspection work of each connected alarm is performed, the number of actually installed alarms can be recognized.
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