PURPOSE: To obtain a highly stable signal by calculating a data for frequency control with a data read from a storage circuit in response to an address signal, converting the calculated data into an analog signal and controlling the oscillating frequency in response to the analog signal.

CONSTITUTION: A time oscillator 2 and a counter circuit 3 are always in operation while receiving power from a battery 1 and the output signal of the counter circuit 3 is the address signal of an arithmetic circuit 5 by a frequency/digital converter 4. The arithmetic circuit 5 receives a data required for the calculation from a storage circuit 6 and the arithmetic circuit 5 makes calculation based on the data of the storage circuit 6 and only the result of calculation corresponding to the address given from the frequency/digital converter 4 is outputted to a D/A converter 8. The D/A converter 8 converts an output signal from the arithmetic circuit 5 into an analog signal and gives the result to a voltage controlled oscillator 9. Thus, a highly stable signal whose frequency change with the lapse of time characteristic is compensated is obtained from an output terminal 11.