STRIKING MECHANISM (Sonnerie au passage)
This type of mechanism strikes the full hours with one or more ding-dongs without indicating the actual hour. Sometimes such watches also strike the half-hours, or even the quarters, in a manner that can be distinguished from the full hours. The sonnerie au passage watch is usually sounded on one or two gongs. In the case of watches striking both the hours and the half-hours, the hours are generally struck on two gongs while the half-hours are struck on a single one, allowing them to be differentiated.
For obvious reasons of comfort, the strike can be activated or deactivated by means of a slide or a pusher.
While alarm watches usually require a dedicated barrel, other types of striking mechanisms consume less energy and draw their power from the barrel driving the movement.