The Bulle clock was produced in large quantities, (around 300,000) in the 1920s and 30s, between the two World Wars. It was invented and first patented in France by Maurice Favre-Bulle and Marcel Moulin, with later assistance from Marius Lavet who was also involved in the early design of the ATO clock.
Bulle clocks have the impulse coil on the pendulum which swings over a fixed magnet, unlike other clocks of the period, e.g. the Brillie and ATO, which have the magnet on the pendulum. The wiring arrangements for the Bulle are therefore more complex as wiring has to be taken down the pendulum.
The pendulum, mounted on a silk suspension, drives a crown wheel one tooth at a time which drives the hands. The pendulum is made up of two rods electrically insulated from each other which carry the current to the coil.
Impulse is given on each left-to-right swing of the pendulum via a silver pin on the pendulum and a 'Y' shaped contact piece which has a silver contact one side of the 'Y' and an insulator the other. The arbor which carries the 'Y' shaped piece drives the pawl and crown wheel. This clock dates from 1934.