Direct current and synchronous motor system

A motor control system in which direct current is sequentially applied to portions of the motor stator windings in response to rotor position signals generated by Hall effect devices until the rotor has reached a desired angular velocity corresponding to the frequency of a source of reference pulses, at which time the portions of the stator windings are driven in a synchronous manner by pulses having a fixed duration and the same frequency as the reference pulses. In the synchronous mode the Hall effect signals are used only in conjunction with circuitry to determine whether or not the rotor is continuing to rotate at the desired, synchronous velocity. The motor is stopped by reverse application of direct current drive to the windings in the direct current drive mode and, again, in accordance with the position signals output from the Hall effect devices. Sine and cosine drive circuitry is disclosed to enable the generation of a substantially continuously rotating magnetic field by the stator windings to allow smooth rotor rotation at very low speeds. Further circuitry is disclosed to provide a hyperbolic variation in the frequency of the reference pulses to allow utilization of the motor system in a disc recording system, whereby substantially constant tangential velocity of a portion of the disc adjacent to a transducer radially movable along the disc is realized by movement by the transducer of a wiper of a linear potentiometer included in the hyperbolic frequency generator circuit.