a switch roller axis 48 on which three switch rollers 50 are mounted in such fashion that they roll on the circumference of switch disks 16 18 and 20 a microswitch 52 is disposed beneath switch arm 44 said microswitch pressing switch arm 44 and hence switch roller 50 against the outer circumference of switch disks 16 18 and 20 with its spring loaded switch pin 54 when due to the different angular velocities of the three switch disks 16 18 and 20 the angular position of the three notches 28 of these switch disks coincide in the angle range of switch roller 50 switch arm 44 with the three switch rollers 50 can drop into the notches 28 actuating microswitch 52 actuation of microswitch 52 turns off the drive in one rotational direction for example this determines one end position of a venetian blind for the second rotational direction of the drive motor an identical shutoff can be provided determining for example the other end position of a venetian blind for this second shutoff an identically constructed arrangement is provided consisting of central gear 30 39 with gear 38 39 and adjustment knob 36 39 as well as planet carriers 2 39 planet gears 14 39 switch disks 16 39 18 39 20 39 switch arm 44 39 and microswitch 52 39 mounted thereon all of these are disposed between the.