To prevent malfunction of a circuit and life deterioration of an electronic apparatus, by obtaining always a constant polarity voltage when the polarity of a battery is changed, by installing four transfer gates wherein a positive voltage setting an input potential as the reference is applied to first gates, a negative voltage is applied to second gates, and the gates open.

A positive polarity battery and a negative polarity battery are connected with a first input terminal IN1 and a second terminal IN2, respectively. A first transfer gate T1 and a fourth transfer gate T4 turn on, and a second transfer gate T2 and a third transfer gate T3 turn off. When a negative polarity battery and a positive polarity battery are connected with the first input terminal IN1 and the second input terminal IN2, respectively, the first transfer gate T1 and the fourth transfer gate T4 turn off, and the second transfer gate T2 and the third transfer gate T3 turn on. Thereby a constant positive voltage and a constant negative voltage are always outputted from a first output terminal OUT1 and a second output terminal OUT2, respectively.