Editing Tuning fork (section)

===In clocks and watches===
[[File:Inside QuartzCrystal-Tuningfork.jpg|thumb|upright|Quartz crystal resonator from a modern [[quartz watch]], formed in the shape of a tuning fork. It vibrates at 32,768 Hz, in the [[ultrasound|ultrasonic]] range.]]
[[Image:Accutron.jpg|thumb|upright|A [[Bulova]] Accutron watch from the 1960s, which uses a steel tuning fork ''(visible in center)'' vibrating at 360&nbsp;Hz.]]
The [[crystal oscillator|quartz crystal]] that serves as the timekeeping element in modern [[quartz clock]]s and [[watch]]es is in the form of a tiny tuning fork. It usually vibrates at a frequency of 32,768&nbsp;Hz in the [[ultrasound|ultrasonic]] range (above the range of human hearing). It is made to vibrate by small oscillating voltages applied by an [[electronic oscillator]] circuit to metal electrodes plated on the surface of the crystal. Quartz is [[piezoelectric]], so the voltage causes the tines to bend rapidly back and forth.

The [[Accutron]], an [[Electromechanical watches|electromechanical watch]] developed by Max Hetzel<ref>{{Patent|ch|312290}}</ref> and manufactured by [[Bulova]] beginning in 1960, used a 360-[[hertz]] steel tuning fork as its timekeeper, powered by electromagnets attached to a battery-powered transistor oscillator circuit. The fork provided greater accuracy than conventional balance wheel watches. The humming sound of the tuning fork was audible when the watch was held to the ear.