The Geneva Wheel
The Geneva wheel is used in cinema film projectors to step the film on one frame at a time. This is a mechanism for intermittent motion.
The lower wheel drives the upper one. The rotational movement of the lower wheel is continuous but the upper wheel only rotates intermittently (in steps). It takes four revolutions of the lower wheel to produce one revolution of the upper wheel.
The drive pin on the lower wheel engages with the slots on the Geneva wheel and make it turn just enough so that it is in position when the pin comes round again.
See the Crank working.