This disclosure pertains to a completely digital, electrically powered servo wherein the servo actuator is minutely incremented at a frequency proportional to the magnitude of an error binary number. The binary error is derived from the difference of a binary reference representing the commanded position of the actuator and a binary feedback representing the position of the actuator. The direction of each increment has the polarity which reduces the difference between the reference and feedback binary numbers. The power unit of the servo is electrohydraulic; however, the servo is entirely electrically controlled and powered. Hydraulic fluid is confined to the power unit where it serves as a link between two solenoid driven piston pumps, a common mode volume adjuster and a hydraulic actuator. The direction the actuator is incremented is dependent on which of the two solenoids the error polarity directs pulsed electrical power.
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