Abstract: A numerical control system having a digitized phase loop comprising a motor for moving an object being controlled, a servo amplifier for driving the motor, feedback means coupled to the motor for generating a first signal indicative of the actual position of the object, and means for converting the first signal to a digital signal indicative of a change in the actual position of the object. Further provided is means for comparing a command digital signal indicative of the desired change in position of the object with the digital signal indicative of the actual change in position of the object to generate an error digital signal and for converting the error signal to an analog signal for driving the servo amplifier.

Abstract: Apparatus for use in a numerical control system for converting a digitial signal, representing a position of a work piece of material being controlled, to an analog signal for driving a servo motor to correct the position of the work piece. The apparatus includes a circuit for converting a digital signal representing the change in the actual position of the work piece to a plurality of signals representative of digital bits of information representing the error in position of the work piece per unit in time. First and second sets of shift registers for receiving the signals representative of digital bits of information, and at least first and second switches are also provided.