| 摘要 |
PROBLEM TO BE SOLVED: To easily increase a power supply series by switching the power supply to the power supply from a battery by making multiple power supply switching relays recover together when one of detection signal is lower than a specific set voltage. SOLUTION: When prescribed source voltages are supplied from all of power supply circuits 1a to 1c, source voltage switch circuits 5a to 5c are all ON and a test switch circuit 7 is also normally ON. The power supply switching relays NV1 to NV3, therefore, operate together to close switching relay contacts nv1 to nv3 to sides (b), so that the electric power is supplied from the power supply circuits 1a to 1c. When the source voltage switch circuits 5a to 5c turn OFF owing to a power failure, etc., of a commercial power source 2, the power supply switching relays NVI to NV3 recover together to close the switching relay contacts nv1 to nv3 to sides (a), so that the power supply is switched to the power supply from a battery 3. At this time, the driving current flowing to a light emitting element 10 from a photocoupler is cut off to stop its light emission. |
