Abstract: A potentiometer includes a rotatably mounted lever which acts as a follower member adapted to lie in contact with a moveable finger, the movement of which the lever is to follow, the lever being biassed at all times towards the finger by resilient return means.The lever is in the form of a fork having two arms whereby it is adapted to embrace the finger. Whichever one of these arms is in the trailing position with respect to the direction of rotation in which the lever is biassed by the return means is longer than the other arm. In the embodiment described, the longer arm is an active arm, the shorter arm being a security arm.

Abstract: A control mechanism for a coupling device such as a clutch or variable speed drive or brake comprises an electric motor. A mechanism links the electric motor to an actuator device for the coupling device. A brake device is coupled to this linking mechanism. The brake device is also coupled to the drive shaft and comprises two friction pads at diametrally opposed positions relative to the drive shaft in contact with the drive shaft. A spring urges the pads towards the drive shaft substantially radially. The brake device comprises a casing rotationally immobilized relative to the drive shaft, which passed through the casing, which encloses the two friction pads. The casing has a back wall and one of the pads is disposed between the drive shaft and this wall. The other pad is slidably disposed in the casing and pressed against the drive shaft by the spring, which is prestressed in compression.