12.000 MHz HC-49U, Crystal resonator

Quartz resonators are designed for use in analog-digital circuits to stabilize and isolate electrical vibrations of a certain frequency or frequency band.
Principle of operation: in a wide frequency band, the resistance of the device has a capacitive character and only at some (working) frequencies has a pronounced resonance (reduction in resistance).
The quartz resonator has better characteristics than other devices for frequency stabilization (oscillatory circuits, piezoceramic resonators): such as stability in frequency (frequency drift) and temperature (resonance frequency change depending on the ambient temperature).
The selective, pronounced resonant nature of the resistance of these components determines the main areas of application of quartz resonators - highly stable clock and reference frequency generators, frequency selection circuits, frequency synthesizers, etc.