| 摘要 |
PURPOSE: To use the power source for replacement of a slave set being charged as the one for backup of a master set in a time of power interruption and to prevent the power source for replacement from being over-discharged. CONSTITUTION: In an ordinary state in which an AC power source 1 is supplied, a CPU 3 sets a transistor Q in an off state, and operates an internal circuit 8 with the AC power source 1. While, when the power interruption occurs in the AC power source 1, a power interruption detection circuit 4 detects the power interruption of the AC power source 1, and outputs a power interruption detection signal to the CPU 3. The CPU 3 sets the transistor Q in an on state based on the power interruption detection signal, and hereinafter, supplies the power source 6 for replacement to the internal circuit 8. Also, when a low level detection signal is outputted from a voltage detection circuit 7 in such state. the CPU 3 sets the transistor Q in the off state, and stops power supply from the power source 6 to the internal circuit 8, which prevents the power sour 6 from being over-discharged. |
