A control apparatus for controlling movement of a hydraulic actuator of a hydraulic control system associated with, for example, an off-road vehicle or a vessel. A geared transmission adapted to be connectable to a support member has rotatable input and output shafts, and a speed ratio of greater than unity and preferably as high as 5 to 10:1. A manually operated steering wheel is supported for substantially free rotation with, the input shaft. A rotatably actuated voltage generator is driven in rotation by the transmission output shaft to produce a high d.c. voltage, low current output signal which is proportional to the speed of rotation of the steering wheel while the output signal polarity is determined by the direction of movement of the steering wheel. A hydraulic valve driver transforms the d.c. output signal into a proportional pulse width modulated voltage control signal which controls position and movement of the hydraulic actuator.