Time signal

A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.

Electrical and electronic time signals

Standard time came into existence in the United States on November 18, 1883. Earlier, on October 11, 1883, the General Time Convention, forerunner to the American Railway Association, approved a plan that divided the United States into several time zones. On that November day, the United States Naval Observatory telegraphed a signal that coordinated noon at Eastern standard time with 11 AM Central, 10 AM Mountain, and 9 AM Pacific standard time.

Related Topics:
Standard time - United States - November 18 - 1883 - October 11 - American Railway Association - Time zone - United States Naval Observatory

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A March, 1905 issue of The Techical World describes the role of the United States Naval Observatory as a source of time signals:

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:One of the most important functions of the Naval Observatory is found in the daily distribution of the correct time to every portion of the United States. This is effected by means of telegraphic signals, which are sent out from Washington at noon daily, except Sundays. The original object of this time service was to furnish mariners in the seaboard cities with the means of regulating their chronometers; but, like many another governmental activity, its scope has gradually broadened until it has become of general usefulness. The electrical impulse which goes forth from the Observatory at noon each day, now sets or regulates automatically more than 70,000 clocks located in all parts of the United States, and also serves, in each of the larger cities of the country, to release a time-ball located on some lofty building of central location. The dropping of the time-ball — accompanied, at some points, with the simultaneous firing of a cannon — is the signal for the regulation by hand of hundreds of other clocks and watches in the vicinity.

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This telegraphic distribution of time signals has been obsoleted by the use of radio.

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Time signal sources that can be used as references for radio clocks include:

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• the WWV, WWVB and WWVH radio stations in the United States
• the CHU radio station in Canada
• the DCF77 radio station in Germany
• the MSF radio station in the United Kingdom

All of these stations now broadcast a time code.

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Loran-C time signals may also be used for radio clock synchronization, by augmenting their highly accurate frequency transmissions with external measurements of the offsets of LORAN navigation signals against time standards.

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The Global Positioning System can also be used as a time reference for radio clocks.

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Many people whose needs do not require precision to the second simply rely on radio broadcasting for time signals. The BBC famously broadcasts "pips" and the strike of Big Ben at the hour in its radio broadcasts.

Related Topics:
BBC - Pips - Big Ben

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