ABSTRACT A device for terminating the rotary movement of a driven shaft after an adjustable predetermined number of revolutions is provided for use in, for example, controlling a venetian blind. The device has first and second switch disks disposed coaxially and having respective notches on their outer circumference. The disks are mounted for coaxial rotation, and drive means drive the disks at different rotational speeds. Switch arm means movably mounted adjacent the disks senses when the notches are in a corresponding angular position for terminating the rotary movement of the driven shaft. The disks have annular openings with internal gear teeth thereon, and the drive means includes an elongated central gear extending coaxially through the annular openings of the disks and adapted to be rotatably driven by the driven shaft. A first planet gear connects the elongated central gear to the gear teeth on the annular opening of the first disk and a second planet gear connects the elongated central gear to the gear teeth on the annular opening of the second disk,the first and second planet gears being rotatably mounted.