A simple adjustable speed reversible drive d.c. motor control system is described. For the purpose of control only one silicon-controlled rectifier is used in conjunction with a single reactor reversible output magnetic amplifier firing circuit. For reliability and long life magnetic amplifier's are incorporated for amplification of the error signal. Reversal of rotation is done by a differential potentiometer and the speed is adjusted to any value from about 10% to rated value by a simple potentiometer. The speed is observed to remain within 2% irrespective of load and line voltage fluctuation