Light responsive apparatus for comparing cards or the like

Claim 1

APPARATUS INCLUDING A FIRST PHOTOVOLTAIC CELL, A SECOND PHOTOVOLTAIC CELL, ELECTRICAL CIRCUITRY RESPONSIVE TO BOTH OF SAID CELLS AND ACTUABLE TO A FIRST CONDITION WHEN NEITHER OF SAID CELLS IS ILLUMINATED OR WHEN BOTH ARE ILLUMINATED, AND TO A SECOND AND DIFFERENT CONDITION WHEN ONLY ONE OF SAID CELLS IS ILLUMINATED, SAID CIRCUITRY INCLUDING A CLOSED LOOP CIRCUIT HAVING SAID TWO PHOTOVOLTAIC CELLS CONNECTED IN SERIES WITH ONE ANOTHER IN ADDITIVE RELATION SO THAT BOTH CELLS TEND WHEN ILLUMINATED TO GENERATE CURRENTS FLOWING IN THE SAME DIRECTION ABOUT SAID LOOP, SAID SERIES CONNECTED CELLS BEING ADAPTED TO PRODUCE A CLOSED CIRCULATION OF CURRENT WITHIN SAID LOOP WHEN BOTH CELLS ARE ILLUMINATED, BUT TO PRODUCE A CIRCULATION OF CURRENT EXTERNALLY OF SAID LOOP WHEN ONLY ONE CELL IS ILLUMINATED, MEANS RESPONSIVE TO SAID EXTERNAL CIRCULATION OF CURRENT, AND RECTIFIER MEANS FOR PREVENTING SAID EXTERNAL CIRCULATION OF CURRENT FROM FLOWING THROUGH SAID LAST MENTIONED MEANS EXCEPT IN A PREDETERMINED SINGLE DIRECTION.