PURPOSE: To realize a crystal oscillator with low power consumption and high stability by using an electronic circuit or the like so as to detect the ambient temperature of the titled crystal oscillator and using an electronic circuit so as to correct the temperature characteristic of the crystal oscillator and an oscillation circuit.

CONSTITUTION: The ambient temperature around a voltage controlled crystal oscillator 1 is converted into an electric signal by a temperature detection element 2, amplified by an amplifier 3 and converted into a digital signal by an A/D converter 4 and the signal is fed to an input/output conversion ROM 5. The input/output conversion ROM 5 is a programmable digital memory to apply the input signal into a specific function and stores data to correct the temperature characteristic of the voltage controlled crystal oscillator 1 as the input/output conversion characteristic. The output signal is given to the voltage controlled crystal oscillator 1 as a voltage signal by a D/A converter 6. Thus, the power to activate the electronic circuits is only one over several hundreds to one over several thousands in comparison with the power to keep the temperature constant by a constant temperature oven or a thermo module.