Method of and apparatus for producing electrical signals representing graphic information

Claim 1

A GRAPHIC INFORMATION TRANSDUCER FOR PRODUCING ELECTRICAL SIGNALS CHARACTERIZING THE MOTION OF A MEMBER IN A PLANE, SAID TRANSDUCER COMPRISING, IN COMBINATION: A PAIR OF INDEPENDENT COILS EACH HAVING A SENSING SECTION WITH SUBSTANTIALLY PARALLEL TURNS LYING IN A PLANE, SAID COILS BEING ARRANGED WITH SAID SENSING SECTIONS SEPARATED FROM ONE ANOTHER AND HELD STATIONARY IN OVERLYING FACE-TO FACE RELATION AND WITH SAID TURNS OF EACH OF SAID SENSING SECTIONS SUBSTANTIALLY PERPENDICULAR TO SAID TURNS OF THE OTHER OF SAID SENSING SECTIONS; AN INPUT MEMBER HAVING AN ASSOCIATED MAGNETIC FIELD WHICH IS SUBSTANTIALLY UNVARYING; AND MEANS PROVIDING A PLANAR SURFACE SUBSTANTIALLY PARALLEL WITH SAID PLANES OF SAID SENSING SECTIONS FOR SUPPORTING SAID INPUT MEMBER FOR MOVEMENT IN THE PLANE OF SAID SURFACE RELATIVE TO SAID SENSING SECTIONS WITH SAID MAGNETIC FIELD INTERSECTING SAID SENSING SECTIONS; SAID INPUT MEMBER BEING FREELY MOVABLE IN SAID PLANE OF SAID SURFACE FOR INDUCING A VOLTAGE IN EACH OF SAID COILS COMMENSURATE WITH THE SPEED OF MOVEMENT OF SAID INPUT MEMBER RELATIVE TO SAID EACH COIL IN A DIRECTION PERPENDICULAR TO SAID TURNS OF SAID SENSING SECTION THEREOF AND CONSTITUTING ONE OF SAID ELECTRICAL SIGNALS.