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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 .
The most accurate pendulum clocks were controlled electrically. [166] The Shortt–Synchronome clock, an electrical driven pendulum clock designed in 1921, was the first clock to be a more accurate timekeeper than the Earth itself. [167] A succession of innovations and discoveries led to the invention of the modern quartz timer.
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).
Developing quartz clocks for the consumer market took place during the 1960s. One of the first successes was a portable quartz clock called the Seiko Crystal Chronometer QC-951. This portable clock was used as a backup timer for marathon events in the 1964 Summer Olympics in Tokyo. [46]
A water clock, or clepsydra (from Ancient Greek κλεψύδρα (klepsúdra) ' pipette, water clock '; from κλέπτω (kléptō) ' to steal ' and ὕδωρ (hydor) ' water '; lit. ' water thief ' ), is a timepiece by which time is measured by the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel, and where the ...
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is an approximate harmonic oscillator: It swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates.
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The Shortt was the first clock to be a more accurate timekeeper than the Earth itself; it was used in 1926 to detect tiny seasonal changes in the Earth's rotation rate. [3] [7] [8] Shortt clocks achieved accuracy of around a second per year, [3] [9] [10] [11] although a recent measurement indicated they were even more accurate. About 100 were ...