"Two kinds of self-controlling machines exist: the regulators whose effect has a fixed value and the Servo-mechanisms whose effect has a value depending on the value of a variable which is the “control.” The idea is simple and reveals itself to be accurate. We have found it confirmed by the technical authority, Prof. Arnold Tustin, of the University of Birmingham, who during the war elaborated a system for the movement of gun turrets and naval guns. According to him, if a machine were entrusted with driving a car, it would be a regulator on a straight road and a servo on a winding one."