| 摘要 |
PURPOSE:To efficiently use a standby unit by activating switchingly an input of an active unit to the standby unit when an alarm is raised from other active unit even when the changeover of an active unit is locked as the result of repetitive changeover. CONSTITUTION:When a unit input 7-1 is interrupted, since an active unit 5-1 outputs an alarm, an alarm reception circuit 6-1 outputs a signal and a switch control section 2-1 switches a changeover switch 1-1 to the position of the standby unit 9. However, the input is interrupted, then the standby unit 9 raises alarm immediately and an alarm reception circuit 10 sends a signal to a switch control circuit 4. When a control section 3 receives the signal, a control signal is sent to the switch control section 2-1 to turn the changeover switch 1-1 to the position of the active unit 5-1. When the control section 3 judges that all active units are not locked, any active unit is judged that it is reciprocated for a prescribed number of times or over with the standby unit for a prescribed time or not. In this case, the changeover switch 1-1 is fixed to the position of the active unit 5-1.
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