Abstract: An apparatus for accurately positioning the support member which is carried by a movable member movable along a trackway or the like comprising a fixed cam having an arcuate surface, at least one cam follower engagable with said cam and means for sensing the position of the cam follower relative to the cam so that when the cam follower has reached a predetermined position along the cam the support member is accurately positioned. A sensing means is disclosed including a cam follower shaft attached to the cam follower. An analog shaft angle resolver is rotatably connected to the cam follower shaft so as to measure the angular rotation of the cam follower shaft and produce a voltage corresponding to the angular rotational position of the cam follower shaft. The analog voltage signal is then converted into a digital signal and fed into a digital display which displays a number proportional to the distance the support member is from a predetermined position.