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This was the mechanism used in the first electric clocks, and is found in antique electric pendulum clocks. It is also found in a few modern decorative mantel and desk clocks. Synchronous clocks These rely on the 50 or 60 Hz utility frequency of the AC electric power grid as a timing source, by driving the clock gears with a synchronous motor ...
Early clock dials did not indicate minutes and seconds. A clock with a dial indicating minutes was illustrated in a 1475 manuscript by Paulus Almanus, [48] and some 15th-century clocks in Germany indicated minutes and seconds. [49] An early record of a seconds hand on a clock dates back to about 1560 on a clock now in the Fremersdorf collection.
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The paper disk or tape had the times pre-printed and the key impressed the key number on the corresponding time. After the shift (or a specified time period, up to 96 hours in the case of the Detex Guardsman clocks), an authorized person (usually a supervisor), would unlock the watchclock and retrieve the disk or tape and insert a new one.
This is an accepted version of this page This is the latest accepted revision, reviewed on 25 February 2025. Type of clock A traditional wind-up (key-wound), mechanical spring-powered alarm clock An alarm clock or alarm is a clock that is designed to alert an individual or group of people at a specified time. The primary function of these clocks is to awaken people from their night's sleep or ...
Telechron—now the "Clock and Timer Division" of GE—declined in the 1950s, mainly because batteries had become much more long-lived and reliable. Battery-powered clocks have the obvious advantage of not depending on the proximity of a power outlet, and do not require the often somewhat unattractive electric cable.
Other uses, most but not all obsolete, include: Wind-up toys – often as a simple mechanical motor, or to create automata. These may be either key-wound, as were many 20th-century model trains, or a simpler pullback motor. Most photographic camera leaf shutters use a clockwork mechanism not unlike that of wristwatches to time the opening and ...
Digital clocks typically use the 50 or 60 hertz oscillation of AC power or a 32,768 hertz crystal oscillator as in a quartz clock to keep time. Most digital clocks display the hour of the day in 24-hour format; in the United States and a few other countries, a commonly used hour sequence option is 12-hour format (with some indication of AM or PM).