Frank Hope-Jones, in collaboration with George B. Bowell, devised the synchronome remontoire in 1895 after a visit to an exhibition to see an installation of a system of electric clocks devised by Van der Plancke of La Precision Cie. , Brussels. The remontoire was first used to rewind the train of a pendulum clock; later, it was arranged to act directly on the pendulum to give an impulse through a roller and pallet. The roller falling off the pallet caused two electrical contacts to close, and an electro-magnet replaced a gravity arm in preparation for the next impulse. A count wheel was used to measure out periods of half-minutes from one impulse to the next, the closing of the contacts also transmitting pulses of current to slave clocks in a system. The synchronome clock became a standard pattern which varied little over a long period of manufacture. It is probably the best known of its type for use as a master clock, and it was sold in greater numbers than any other thanks to the publicity measures of Hope-Jones. In 1921 it was used by William Hamilton Shortt as the slave clock for his 'free-pendulum clock', installed in Edinburgh Observatory. An accuracy of less than one-tenth of a second a day error was achieved, ousting the Riefler regulator clocks from observatories all over the world.