Numerical position control system

Claim 1

A NUMERICAL CONTROL SYSTEM FOR CONTROLLING THE POSITION OF STRUCTURE, COMPRISING A NUMBER OF CONTROL SHAFTS COUPLED WITH EACH OTHER AT A FIXED TRANSMISSION RATIO SO AS TO BE DIGITALLY RELATED TO EACH OTHER; POSITION DETECTING MEANS MOVABLE IN ACCORDANCE WITH POSITIONAL CHANGE OF THE STRUCTURE TO BE CONTROLLED, A NUMBER OF DETECTOR SHAFTS COUPLED WITH SAID DETECTING MEANS AND COUPLED WITH EACH OTHER AT A FIXED TRANSMISSION RATIO SO AS TO BE DIGITALLY RELATED TO EACH OTHER; EACH OF SAID CONTROL SHAFTS BEING COAXIALLY ALIGNED WITH ONE OF SAID RESPECTIVE DETECTOR SHAFTS; A NUMBER OF PHOTOELECTRIC DEVICES EACH HAVING TWO DISCS COAXIALLY MOUNTED ON ONE OF SAID RESPECTIVE CONTROL SHAFTS AND THE ONE ALIGNED DETECTOR SHAFT RESPECTIVELY, ONE OF SAID DISCS HAVING MOUNTED THEREON A LIGHT SOURCE POSITIONED ON ONE SIDE OF SAID OTHER DISC AND THREE RADIALLY ALIGNED PHOTOSENSITIVE DEVICES ON THE OTHER SIDE OF SAID DISC, SAID OTHER DISC DEFINING THREE ARCUATE APERTURES AT DIFFERENT RESPECTIVE RADII AND OCCUPYING MUTUALLY EXCLUSIVE SECTORS, TWO OF SAID ARCS BEING SUBSTANTIALLY SEMICIRCULAR AND THE THIRD BEING SMALL RELATIVE TO THE OTHER TWO, WHEREBY SAID PHOTOSENSITIVE DEVICES ISSUE A CORRECTIVE OUTPUT SIGNAL WHEN THE INSTANTANEOUS ANGULAR POSITION OF ONE DISC DEPARTS FROM THAT OF THE OTHER.