| 摘要 |
PROBLEM TO BE SOLVED: To raise reliability by extending a remaining period until a battery becomes dead as much as possible, even if a low battery alarm is given. SOLUTION: A low battery monitoring part 60, when detecting a low battery due to voltage drop of a battery power supply, outputs the low battery alarm that intermittently indicates an interlocking source and transmits an event signal which indicates the low battery to other alarms, and meanwhile when receiving the event signal which indicates the low battery from the other alarms, and outputs the low battery alarm which intermittently indicates an interlocking destination. A transmission and receiving time control section 62, when detecting the low battery, changes a receiving period of a receiving circuit 44 into a long period, and meanwhile when receiving the event signal which indicates the low battery from the other alarms, changes transmission time of a transmission circuit 42 into transmission time of equal to or more than the long receiving period after the change. COPYRIGHT: (C)2011,JPO&INPIT
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