Electrical indicating instruments for use with progressively varied outputs

Claim 1

AN ELECTRICAL INDICATING INSTRUMENT COMPRISING A MAGNET SYSTEM INCLUDING A CYLINDRICAL CORE SURROUNDED BY AN ANNULAR AIR GAP, A COIL ANGULARLY DISPLACED ABOUT THE AXIS OF SAID CORE TO MOVE IN SAID AIR GAP SUBSTANTIALLY PROPORTIONALLY TO THE INSTANT MAGNITUDE OF AN ELECTRIC CURRENT WHICH IS PROGRESSIVELY VARIABLE IN MAGNITUDE IN A PLURALITY OF DISCRETE STEPS AND IS SUPPLIED TO AID COIL, A LIGHT SOURCE, A VIEWING SCREEN, OPTICAL MEANS FOR DIRECTING LIGHT FROM SAID SOURCE TOWARD SAID SCREEN IN THE FORM OF A BEAM, A SCALE OPERATIVELY ASSOCIATED WITH SAID COIL AND MOVABLE THEREWITH, SAID SCALE HAVING A CURVED ZONE WHICH IS TRAVERSED THROUGH SAID BEAM AS SAID COIL IS ANGULARLY DISPLACED, LIGHT-TRANSMITTING AND OPAQUE AREAS IN SAID ZONE DEFINING SYMBOLS EACH REPRESENTATIVE OF A DIFFERENT MAGNITUDE OF SAID ELECTRIC CURRENT, SAID AREAS BEING SO SPACED THAT THE SYMBOL APPROPRIATE TO THE INSTANT MAGNITUDE OF SAID CURRENT WILL BE BROUGHT INTO SAID BEAM BY THE PASSAGE OF SAID CURRENT THROUGH SAID COIL, AN ELEMENT OF MAGNETISABLE MATERIAL OPERATIVELY CONNECTED WITH SAID SCALE TO BE MOVED THEREBY IN A GIVEN PATH AS SAID COIL IS ANGULARLY DISPLACE, AN ELECTROMAGNET FIXEDLY MOUNTED IN PROXIMITY TO SAID MAGNET SYSTEM, POLEPIECES ON SAID ELECTROMAGNET DISPOSED UPON OPPOSITE SIDES OF SAID GIVEN PATH TO DEFINE BETWEEN THEM AN AIR GAP CONTAINING SAID GIVEN PATH AND TEETH FORMED ON ONE AT LEAST OF SAID POLE-PIECES TO NARROW SAID SECOND-MENTIONED AIR GAP AT PREDETERMINED LOCATIONS ALONG SAID GIVEN PATH EACH DEFINING A POSITION OF SAID ELEMENT IN WHICH A DIFFERENT ONE OF SAID SYMBOLS IS ACCURATELY POSITIONED IN SAID LIGHT BEAM.