Abstract: A shaft is supported rotatably within a tubular aluminum extrusion and is rotated by a motor, with at least a portion of the length of the shaft comprising a lead screw along which a nut is displaced during rotation of the shaft, with a member projecting from the nut radially of the shaft and through a slot in the extrusion. The projecting member provides a linearly movable indicator for measurement and/or control of the direction and amount of rotation of the shaft. For measurement purposes, a simple scale or more elaborate linear encoder may be situated at the slot for cooperation with the moveable member. For control purposes, proximity switches are adjustably repositionable along the slot so as to establish limits by and in response to which a controller may control the rotation.