The constant temperature crystal oscillator is referred to as the constant temperature crystal oscillator. The English abbreviation is OCXO (Oven Controlled Crystal Oscillator). The temperature of the quartz crystal resonator in the crystal oscillator is kept constant by the constant temperature bath, and the variation of the oscillator output frequency caused by the change of the ambient temperature is reduced. To the smallest crystal oscillator. The OCXO is composed of a thermostat control circuit and an oscillator circuit.