Input: green shaft.
Output: yellow shaft. It rotates only when the input rotates at prescribed speed V. Here the output speed = V/2
Brown semi-clutch of friction cone under pressure of blue spring makes pink gear rotate.
Centrifugal governor of two violet balls makes orange slider go up-down subject to the input speed. The governor is set in such a way that at prescribed input speed V the cam of orange slider does not contact blue angular arms and the brown semi-clutch can transmit motion to output shaft via pink gear. When the input speed is larger or smaller than V, the cam turns the blue angular arms to pull the brown semi-clutch from contact with the pink gear and the output shaft stops.
The video was made following a request from a YouTube viewer.