A throttle control cartridge has a circuit board carrying a Hall-effect sensor, the position of which is fixed in a housing carrying a cam. A shaft carrying a magnet is rotatably and translatably disposed with respect to the housing and carries a cam follower that engages the cam and translates the shaft with respect to the housing when the shaft is rotated with respect to the housing in at least one of two opposed angular directions. The cam and the cam follower have at least first and second pairs of cam surfaces in which a first cam surface is disposed at a different cam or helix angle then the second cam surface. A redundant stop is cooperatively formed between the cam follower and splines on the shaft to limit axial translation of the cam follower in one direction of rotation of the shaft relative to the housing.