Gregory's Server
This diagram shows the servo loop. A sensitive inductive pickup detected the rotation and generated an error signal that went to an amplifier. The motor rotated to counteract the bellows motion. When the error signal was 0, the output shaft rotation matched the pressure. 5/13
The amplifier took three boards: transistors in conjunction with magnetic amplifiers (yellow units). Transistors weren't good enough at the time to drive the motors directly, so transistors controlled the magnetic amplifiers, which drove the motors. 6/13