- A quartz crystal is held between two electrodes. The piezo-electric effect which converts a mechanical stress into a voltage and vice versa results in a high-Q tuned circuit
- In addition to resonance at its fundamental frequency the crystal can vibrate and exhibit resonance on overtones (odd harmonics)
- Typical uses are in a tuned circuit in an oscillator to provide accurate and stable frequency output
- Also used as resonant element in filters