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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.
In electric clocks, the power source is either a battery or the AC power line. In clocks that use AC power, a small backup battery is often included to keep the clock running if it is unplugged temporarily from the wall or during a power outage. Battery-powered analog wall clocks are available that operate over 15 years between battery changes.
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).
These keep time by counting the oscillations of a calibrated tuning fork with a specific frequency. These were only made in battery-powered form. Battery-powered clocks have been made using the schemes above with the obvious exception of a synchronous movement. All battery-powered clocks have been largely replaced by the lower cost quartz movement.
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It is also possible for quartz clocks and watches to have their quartz crystal oscillate at a higher frequency than 32 768 (= 2 15) Hz (high frequency quartz movements [4]) and/or generate digital pulses more than once per second, to drive a stepping motor powered second hand at a higher power of 2 than once every second, [5] but the electric ...
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