Greenwich Time Signal

Series of six pips broadcast by the BBC

The Greenwich Time Signal (GTS), popularly known as the pips, is a series of six short tones broadcast at one-second intervals by many BBC Radio stations to mark the precise start of each hour. The pips were introduced in 1924, generated by the Royal Observatory, Greenwich, and from 1990 were generated by the BBC in London. The broadcast pips replaced an electrical time coordination system based on the railway telegraph network, which itself was an extension of the mechanical time balls in Portsmouth (1829) and later Greenwich (1833), which enabled navigators aboard ships moored in those places to set their chronometers for the determination of longitude on voyages.

This keyword could refer to multiple things. Here are some suggestions: