PURPOSE: To minimize the power consumption by feeding an oscillation circuit with the voltage once dropped below the specified level employing a lithium battery easy to provide specified voltage for the power source.

CONSTITUTION: When a clear switch 9 is operated after mounting of the 3V lithium battery 1, the operation signal AC clears a divider circuit 6 a and time counting circuit 7 while the output voltage Vss of the battery 1 is outputted from the output terminal V2 of a voltage lowering circuit 2 and fed to the oscillation circuit 3 the first divider circuit 4. The divider circuit 4 produces signal of 512Hz to be fed to the voltage lowering circuit 2 following a proper level shift 5. According to the signal of 512Hz, the voltage lowering circuit 2 switches the connection of internal capacitors so that the output voltage V1 of 1/2Vss and the output voltage V2 of 1/4Vss are outputted to be separately fed to a liquid crystal display 8, the oscillation circuit 3 and the first divider circuit 4.