The clock by the gate was probably the first to display Greenwich Mean Time to the public, and is unusual in using the 24-hour analog dial.His idea was to use what he called "galvanism" or electric signalling to transmit time pulses from Greenwich to other clocks throughout the country, and perhaps to Europe and the colonies too.In 1849 Charles Shepherd Junior (1830–1905),[2] an engineer and son of a clockmaker, patented a system for controlling a network of sympathetic clocks using electricity (or galvanism, as it was called).Airy also wanted the existing Greenwich time ball to be electrically operated, so that its descent at 13:00 was synchronised with the motor clock inside the observatory.The Gate Clock originally indicated astronomical time, in which the counting of the 24 hours of each day starts at noon.The clock was changed in the 20th century to indicate Greenwich Mean Time, in which the counting of the 24 hours of each day starts at midnight.On 15 October 1940, during the World War II Blitz, the dial was damaged by a bomb, but the mechanism survived.
