Time signal
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A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.
These automatic signal clocks were synchronized by telegraphy in 1905 before the widespread use of radio
A RBL 40-pounder Armstrong gun being fired as "the one o'clock gun" on Woolwich Common, circa 1905
The time ball on the roof of Greenwich Observatory, London
A modern LF Radio clock
Time ball
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A time ball is a large, wooden or metal ball that moves up and down a pole, and which is dropped at a predetermined time of day. Because precise timekeeping is essential to the determination of longit
Time signal
…signals enabled greater precision than audible ones, although audible signals could operate better under conditions of reduced visibility. The first time ball was erected at Portsmouth, England in 1829 by its inventor Robert Wauchope. One was installed in 1833 on the roof of the Royal Observatory in Greenwich…
The Boston Time Ball (1881)
Sydney Observatory with time ball
The time ball at Port Lyttelton, New Zealand, started signalling Greenwich Mean Time to ships in the harbour beginning in 1876. The Lyttelton Timeball Station was destroyed by an earthquake in 2011 but was rebuilt and reopened in 2018.