Torque limiter

Because there is no mechanical contact between the two shafts, they are also used to transmit torque through a physical barrier like a thin plastic wall.

It can have single or multiple detent positions, or a snap acting spring which requires a manual reset.

It may be a part of an assembly of multiple gearsets used to primarily reduce speed and multiply torque as well as perform ratio changes.

A series of ball detents act on the annulus to lock it, allowing power to be transmitted from the planet carrier to the sun gear.

This system equally limits torque in both directions of rotation and also works with the sun gear as the input.

A simple example is found in a fixed-spool fishing reel, where the slipping torque is set by means of a large hand nut in order that the reel will turn and allow more line to unwind before the line breaks under the pull of a fish.