Abstract: Adjustable cam actuated switch mechanism of the type in which the switch is operated by a rotating cam means on a timing shaft. The cam means includes a cam plate that is rotatable relative to the timing shaft and the cam plate is adjustably connected to the shaft through a differential gear mechanism including a pair of spur gears of like pitch diameter but having relatively different number of teeth, one of which is drivingly connected to the timing shaft and the other of which is drivingly connected to the cam plate and a pinion gear that meshes with both spur gears and is carried by a housing that encloses the spur gears and which is rotatable relative to the timing shaft to angularly adjust the cam relative to the shaft.