Ever wondered what the famous pip-pip-pips sound heard on BBC radio marking the hour is?
Known originally as the Eight-day wall-mounted astronomical regulator, the clock is perhaps more commonly known as the pip-pip clock.
This astronomical regulator was originally made for use in observing the Transit of Venus in 1874.
In 1923 it became the source of the six-pip time signal used by the BBC. The clock sent electrical impulses down a telephone wire to the BBC for conversion into audio pips for radio broadcasts.
The clock was used for the pips from 1924 to 1990.