Crystals are naturally occurring materials that can be induced to resonate (vibrate) at an exact frequency. Quartz, a piezoelectric crystal that provides excellent mechanical and electrical stability, acquires a charge when compressed, twisted, or distorted.
Oscillators are devices that are used to generate repetitive signals. They produce output signals without an input signal. There are two major types of electronic oscillators: harmonic oscillators and relaxation oscillators. Harmonic oscillators produce sine wave outputs. Relaxation oscillators produce non-sine wave outputs such as square wave, rectangular wave, and sawtooth outputs.
