PURPOSE: To preserve the steady operation of the load even in case the battery voltage drops by forming the voltage reduction means for the battery power source with the 1st means consisting of two units of capacitors plus the 2nd means comprising two units of resistances and then driving the load with the combination of both means.

CONSTITUTION: For the voltage reduction circuit of the battery power source which is used to the electronic watch unit, signal l features a low level when the illumination lamp is not driven. And battery voltage V1 is divided by capacitors 17 and 18, and voltage V3 and V4 of output terminals I and II are lowered down to 1/2V1 each to be supplied to the common signal generator circuit, the oscillator circuit, the logic circuit and others. While voltage V1 drops greatly when the lamp is driven. In that case, signal l features a high level, and voltage V4 given from terminal II is delivered in the form of voltage V1 to be supplied to the oscillator and logic circuits. Voltage V3 of terminal I is divided by resistances R1 and R2 down to 1/2V1 to be supplied to the common signal generator circuit. Accordingly, the oscillator and logic circuits can be driven with the voltage equal to the battery voltage when the lamp is driven, thus preventing the malfunction or the oscillation stop for the circuits.