The Synchronome Clock is a very interesting variation on the gravity escapement where the restoration of the gravity arm is accomplished by an armature that is in turn energized by a switch that is tripped by the fall of the gravity arm. The gravity arm is released by a 15 tooth index wheel driven by the pendulum that releases the gravity arm catch every 30 seconds.
The index wheel is driven by a jewel pallet and the entire assembly is as light as possible to minimize interference with the highly detached pendulum.
The dial is a separate mechanism that operates via a ratchet and a solenoid that is synchronized with the armature that raises the gravity arm. The entire system is current driven so as many slaves as desired can be synchronized from a given master. If the number of slaves becomes very large, the system uses some of the slaves as boosters with an auxiliary power source and another switch.
When this mechanism is combined with a second clock that receives impulse without indexing its own wheel and the two clocks contain a synchronizing circuit, the result is the Shortt Free Pendulum clock. The Shortt Free Pendulum was the timekeeping reference standard around the turn of the 20th century.
I purchased this clock on Portobello Road in London on September 15th, 2001. I had been scheduled to come back to Boston on September 11th and was at Gatwick Airport waiting to board my flight when the horrific events of that day took place.