Escapement

An escapement is a mechanical linkage inside watches and clocks that regulates timekeeping by controlling how the gear train advances, giving small pushes to an oscillating element such as a pendulum or balance wheel while periodically releasing a tooth of the escape wheel to let the gear train move forward at a steady rate. This dual action both restores energy lost to friction and produces the ticking sound characteristic of mechanical clocks. The first mechanical escapement, the verge escapement, appeared in thirteenth century medieval Europe and marked a major advance, allowing clocks to move away from continuous flow devices like water clocks toward oscillatory timekeeping. Earlier liquid driven escapements existed in ancient Greece and China but depended on the rate of fluid flow and were far less precise, and after the pendulum was introduced around 1657 escapement design advanced rapidly, with more than 300 variants developed by the nineteenth century even though only about ten of them ever saw widespread commercial use.