An apparatus including a rotary knob (14) coupled to the shaft of the rotor of a stepper motor having first and second stator windings, in quadrature, each winding having a grounded center tap to provide first and second winding portions for each winding. One pair of first winding portions is used for providing pulse inputs to a microprocessor (20) on rotation of the knob, in either direction, via a pulse control system (22), the microprocessor providing command signals to a braking control system (24). On command of the processor, a force or torque is applied to the rotor, by means of energization of the other pair of winding portions, the force being in opposition to the direction of rotation of the knob. Under control of the microprocessor, the force may be intermittently applied to simulate a mechanical detent arrangement, or be a constant force for braking.