OCXO is a crystal oscillator that keeps the temperature of quartz wafers basically unchanged by placing them in a constant temperature tank. It usually uses high precision SC cut type and low cost AT cut type quartz wafer oscillator. HCI constant temperature crystal oscillator can achieve frequency stability of 10-9 magnitude, and has extremely low aging rate and phase noise, very high short stability and seismic and acceleration characteristics, widely used in communication base station, microwave radar, precision instruments, telemetry, navigation and other fields.