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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).
The master clock in a clock network can receive accurate time in a number of ways: through the United States GPS satellite constellation, a Network Time Protocol server, the CDMA cellular phone network, a modem connection to a time source, or by listening to radio transmissions from WWV or WWVH, or a special signal from an upstream broadcast network.
Slave clocks either kept time by themselves, and were periodically corrected by the master clock, or required impulses from the master clock. Many slave clocks of these types were in operation, most commonly in schools, offices, military bases, hospitals, railway networks, telephone exchanges and factories the world over. [ 2 ]
A common misconception is that a digital clock is more accurate than an analog wall clock, but the indicator type is separate and apart from the accuracy of the timing source. Talking clocks and the speaking clock services provided by telephone companies speak the time audibly, using either recorded or digitally synthesized voices .
Lenzkirch Clock Co (Aktiengessellschaft fur Ukrenfabrikation) (1851-1929) factory operated by Junghans 1929-1932; Mauthe Clock Company (c1870 - 1976) Jakob Schlenker Grusen, Schwenningen (JSGUS/ISGUS) (1888–present) Johannes Schlenker, Schwenningen (1822-1883) then Schlenker and Kienzle (1883-1897) then Kienzle
The Standard Electric Time Company was a Springfield, Massachusetts company founded in 1884, and was a manufacturer of synchronized clock systems and fire alarm systems. They were the oldest manufacturer of electric clocks in the United States. The company was acquired by Johnson Controls in 1970 and then Faraday in 1978.
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