| 摘要 |
PROBLEM TO BE SOLVED: To improve detection accuracy of power-failure. SOLUTION: An alternating current voltage monitoring circuit 62 comprises a level detecting circuit 62a comprising a transistor supplied with 24 V alternating current power from a 24 V alternating current power supply 51 and a resistor, a level adjusting circuit 62b capable of changing a reference voltage of the level detecting circuit 62a, a timer circuit 62c connected to an output of the level detecting circuit 62a and comprising two mono stable multi vibrators, and a time constant setting circuit 62d for adjusting a timer operation period of the timer circuit 62c by changing time constant, comprising a resistor and a capacitor. A power failure detecting signal is outputted from the timer circuit 62c to a power down reset circuit 65, a signal for validating the power failure detecting signal as a timing of backing up data on a game state, namely NMI, is outputted based on an alternating current waveform, and when a 24 V alternating current signal is short of one cycle, the power failure is determined.
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