Abstract: The motor is to be controlled to execute steps having a preselected step length. A displacement transducer is coupled to the motor and furnishes a displacement signal having a constant first predetermined value during motor movement by a predetermined fraction of said step length and changes to a second predetermined value during motor movement by the remainder of the step length. A voltage divider circuit and a differentiator circuit are connected to the output of the transducer and furnish a proportional and a differentiated signal. The two signals are combined in an operational amplifier whose output serves as a control signal for controlling the operation of the motor. The transducer includes three light transmitter-receiver pairs which are switched on in a first sequence when the motor rotates in one direction and in a second sequence for rotation in the opposite direction.