Clock
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A clock or chronometer is a device that measures and displays time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such a
An analog pendulum clock made around 18th century
Casio F-91W digital watch, a historically popular watch introduced in 1989
Simple horizontal sundial
The flow of sand in an hourglass can be used to keep track of elapsed time.
Quartz clock
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Quartz clocks and quartz watches are timepieces that use an electronic oscillator regulated by a quartz crystal to keep time. The crystal oscillator, controlled by the resonant mechanical vibrations o
Clock
…was invented in 1917 by Alexander M. Nicolson, after which the first quartz crystal oscillator was built by Walter G. Cady in 1921. In 1927 the first quartz clock was built by Warren Marrison and J.W. Horton at Bell Telephone Laboratories in Canada. The following decades saw the development of quartz clocks as…
A basic analog quartz clock
Modern quartz wristwatch
Circuit board of an e block from a chronograph-wristwatch. The quartz crystal oscillator can be seen on right.
Disassembled analog quartz clockwork; quartz crystal oscillator (top left), Lavet-type stepping motor (left) with a black rotor sprocket and connected white and transparent gears (right). These gears control the movement of the second, minute and hour hands.