Lever escapement "draw" its action is very precise. Third, it is self-starting, so if the watch is jarred in use so the balance wheel stops, it will start again. A cheaper and less accurate version of the lever escapement, called the pin pallet escapement, invented by Georges Frederic Roskopf in 1867, is used in clocks and timers. The escape wheel is geared to the watch's wheel train, which applies torque to it from the mainspring. The rotation of the escape wheel is controlled by the pallets. The escape wheel has specially shaped teeth of either ratchet or club form, which interact with
Escapement to a point close to its unstable state, and is released with a snap each swing of the balance wheel to give the wheel an impulse, after which it is cocked again by the wheeltrain. The advantage claimed is that since the blade imparts the same amount of energy to the wheel each release, the balance wheel is isolated from variations in impulse force due to the wheeltrain and mainspring which cause inaccuracies in conventional escapements. Parmigiani Fleurier with its Genequand escapement and Ulysse Nardin with its Ulysse Anchor escapement have taken advantage of the properties of silicon flat springs.