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History of timekeeping devices. A marine sandglass. It is related to the hourglass, nowadays often used symbolically to represent the concept of time. The history of timekeeping devices dates back to when ancient civilizations first observed astronomical bodies as they moved across the sky. Devices and methods for keeping time have gradually ...
The word clock derives from the medieval Latin word for 'bell'— clocca —and has cognates in many European languages. Clocks spread to England from the Low Countries, [6] so the English word came from the Middle Low German and Middle Dutch Klocke. [7]
A unit of time is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI), and by extension most of the Western world, is the second, defined as about 9 billion oscillations of the caesium atom. The exact modern SI definition is " [The second] is defined by taking the fixed numerical value of the ...
Automaton clocks are clocks which feature automatons within or around the housing and typically activate around the beginning of each hour, at each half hour, or at each quarter hour.
This is a list of clocks that have attained notability because of their historical importance, accuracy, exceptional artistry, architectural value, or size.
A world clock is a clock which displays the time for various cities around the world. The display can take various forms: The clock face can incorporate multiple round analogue clocks with moving hands or multiple digital clocks with numeric readouts, with each clock being labelled with the name of a major city or time zone in the world. The World Clock in Alexanderplatz displays 146 cities in ...
Clock signal. In electronics and especially synchronous digital circuits, a clock signal (historically also known as logic beat) [1] is an electronic logic signal (voltage or current) which oscillates between a high and a low state at a constant frequency and is used like a metronome to synchronize actions of digital circuits.
Radio clock. A modern LF radio-controlled clock. A radio clock or radio-controlled clock (RCC), and often colloquially (and incorrectly [1]) referred to as an "atomic clock", is a type of quartz clock or watch that is automatically synchronized to a time code transmitted by a radio transmitter connected to a time standard such as an atomic clock.