The full name is quartz crystal oscillator, its role is to generate the original clock frequency, this frequency after the frequency generator amplification or reduction into a computer in a variety of different bus frequencies. Crystal oscillator is also divided into quartz crystal resonator and quartz crystal oscillator. 

The role of the crystal oscillator
1, to the normal operation of the microcontroller to provide a stable clock signal.
 Principle: in the quartz crystal on the two pole plate plus an electric field, the chip will produce mechanical deformation, the pole plate to apply mechanical force to make it deformed, and will produce the corresponding charge on the pole plate, which is called the piezoelectric effect. If in the two pole plate plus alternating voltage, the wafer will produce mechanical deformation vibration, at the same time this mechanical vibration will also produce alternating electric field (relatively small), but when the frequency of the applied alternating voltage and the wafer's intrinsic frequency (determined by its shape and size) is equal, the amplitude of the mechanical vibration will be aggravated to produce the alternating electric field also increased. These are called piezoelectric harmonics.

2, even if the removal of the crystal, the circuit can still oscillate, and if the two capacitors into adjustable capacitors can also get the desired frequency, that also need crystal to do: crystal, ceramic resonator slot, RC oscillator and silicon oscillator is suitable for micro-controllers are four kinds of clock source. Optimising the clock source design for a specific application depends on the following factors: cost, accuracy and environmental parameters. RC oscillators can be started up quickly and at a relatively low cost, but typically have poor accuracy over the full temperature and operating supply voltage range, varying from 5% to 50% of the nominal output frequency; however, oscillators based on crystals and ceramic resonant slots typically offer very high initial accuracy and low temperature coefficients compared to RC oscillators. initial accuracy and low temperature coefficients compared to RC oscillators.

Product Use:

1, general-purpose crystal oscillator, used in various circuits, to generate oscillation frequency. 
2, Quartz crystal resonator for clock pulse, with other components to produce standard pulse signals, widely used in digital circuits.
3、Quartz crystal resonator for microprocessor. 
4, CTVWVTR quartz crystal resonator. 
5, Quartz crystal oscillator for clocks and watches.