This model shows how the verge escapement with foliot regulator works.
The escapement is the mechanism that lets “escape,” that is, “releases” part of the motive force at regular intervals, allowing the periodic motion of the regulator to continue.
“Foliot,” a term derived from French, means “rod balance” and indicates one of the earliest types of regulator device. The mechanism consists of a toothed crown wheel (escapement) which engages the verge levers connected to the “foliot” alternatively. The levers lock and release the crown wheel one at a time, making it advance at regular intervals.