How the synchronome remontoire led to improvements in time-keeping accuracy

Within the Institution’s artefact collection is the synchronome remontoire mechanism removed from the original transmitter clock installed in One Birdcage Walk when it opened in 1899.

The mechanism, also known as an electrically maintained or driven pendulum, was created by horologist Frank Hope-Jones and led to improvements in time-keeping accuracy. The synchronome remontoire used a gravity arm reset by an electro-magnet to impulse the pendulum. This impulse would occur every 30 seconds. Hope-Jones realised that the impulse could not only drive the hands of the transmitter clock but also those of multiple receiver clocks too. This led to the system that was installed at One Birdcage Walk. The main transmitter clock governed the time shown by all the clocks.

The synchronome remontoire contributed to the development of the Shortt free-pendulum clock installed at the Royal Observatory, Greenwich in 1924 and subsequently in the principal observatories of the world until it was superseded by quartz and atomic clocks.

The synchronome remontoire can be viewed here.