Between May 1861 and June 1862 the Hourly Signal Relay, manufactured by William Morris and Henry Mapple, was added to the time signal apparatus of the Royal Observatory.
The relay was intended to relieve the mechanism of the Ball-detent which also dropped the Greenwich Time Ball. According to George Biddell Airy (Astronomer Royal 1835-1881) ‘mechanical mismanagement’ of the Ball-detent had been the source of numerous errors in hourly signals. This relay separated the impulse of the electromagnet for the Greenwich time-ball from the external galvanic connections of the Observatory.
Each hour the mean time clock (Shepherd’s Motor Clock) activated an electromagnet inside the relay. This electromagnet in turn closed six separate contacts which sent time signals along six corresponding lines of telegraph wire. At various times after 1861 these connections were made with the London and South Eastern Railway Company, the General Post Office, and the Deal time-ball.
The relay remained in service until at least 1881, when an illustration of it was published alongside the other time signal apparatus of the Computing room in an appendix to the 1879 Greenwich Observations.
The makers of the relay, William Morris and Henry Mapple, who together held a patent for electric timekeeping (A.D. 1860, 22nd June. No. 1515 “Electric Clocks and Telegraphs”). Henry Mapple a former telegraph engineer for the Electric Telegraph Company exhibited several pieces an electric telegraph, a clock escapement, and a telegraphic fire alarm at the Great Exhibition of 1851.