Radiation-controlled variable resistance

Claim 1

A SYSTEM FOR DEVELOPING AN ELECTRICAL SIGNAL REPRESENTING THE POSITION OF A MOVABLE MEMBER, SAID SYSTEM COMPRISING IN COMBINATION A LAYER OF SOLID PHOTOCONDUCTIVE MATERIAL HAVING TWO OPPOSITE FACES, AN ELONGATED RESISTIVE ELEMENT IN DIRECT ELECTRICAL CONTACT WITH ONE OF SAID FACES, A CONDUCTIVE ELEMENT IN DIRECT ELECTRICAL CONTACT WITH THE OTHER FACE IN SPACEDLY OPPOSED RELATION TO THE RESISTIVE ELEMENT, AT LEAST ONE OF SAID ELEMENTS BEING CAPABLE OF TRANSMITTING INCIDENT RADIATION TO THE PHOTOCONDUCTIVE LAYER, THE BODY OF THE PHOTOCONDUCTIVE LAYER HAVING A VOLUME RESISTANCE TO CURRENT FLOW IN BOTH DIRECTIONS BETWEEN SAID ELEMENTS THAT IS RELATIVELY HIGH IN THE DARK AND RELATIVELY LOW WHEN IRRADIATED, MEANS FOR SUPPLYING DIFFERENT AND SUBSTANTIALLY CONSTANT ELECTRICAL VOLTAGES TO THE RESPECTIVE END PORTIONS OF THE RESISTIVE ELEMENT TO ESTABLISH THEREIN AN ELECTRICAL POTENTIAL THAT VARIES LONGITUDINALLY SUBSTANTIALLY INDEPENDENTLY OF ELECTRICAL CONDUCTION IN THE PHOTOCONDUCTIVE LAYER, MEANS FOR SELECTIVELY IRRADIATING A NARROW ZONE OF THE PHOTOCONDUCTIVE LAYER THAT EXTENDS CONTINUOUSLY BETWEEN SAID ELEMENTS, THE LAST SAID MEANS BEING ACTUABLE TO VARY THE LONGITUDINAL POSITION OF THE IRRADIATED ZONE IN RESPONSE TO MOVEMENT OF SAID MOVABLE MEMBER, AND MEANS FOR TAPPING FROM THE CONDUCTIVE ELEMENT A VOLTAGE SIGNAL THAT REPRESENTS SUBSTANTIALLY THE VALUE OF SAID POTENTIAL AT THE IRRADIATED ZONE.