How are pendulum clocks powered?

Written and fact-checked by The Editors of Encyclopaedia Britannica

Pendulum clocks are powered by mechanisms that trigger the pendulum to swing with a constant period. Traditionally, weight or spring mechanisms fulfill this purpose, but some clocks use electricity to power the pendulum. Weight-powered pendulum clocks require rewinding when their weights are fully lowered, while the spring-powered variety must be recoiled once the springs extend.