Light sensitive alarm system

Claim 1

IN AN ALARM CIRCUIT HAVING A FOUR TERMINAL WHEATSTONE BRIDGE NETWORK, THE IMPROVEMENT COMPRISING A SINGLE SOURCE OF LIGHT ENERGY, A PLURALITY OF PAIRS OF SIMILAR LIGHT SENSITIVE MEANS IN WHICH THE MEMBERS OF EACH PAIR ARE PHYSICALLY ADJACENT EACH OTHER AND IN WHICH THE PAIRS ARE PHYSICALLY SPACED FROM EACH OTHER A SUBSTANTIAL DISTANCE, A DIRECT CURRENT SOURCE CONNECTED ACROSS THE TWO INPUT TERMINALS OF SAID BRIDGE, CURRENT RESPONSIVE MEANS CONNECTED ACROSS THE TWO OUTPUT TERMINALS OF SAID BRIDGE, MEANS FOR CONNECTING A LIGHT SENSITIVE MEMBER OF ONE PAIR IN ONE LEG OF THE BRIDGE AND THE OTHER LIGHT SENSITIVE MEMBER OF SAID ONE PAIR IN A LEG OF THE BRIDGE DIAGONALLY OPPOSITE SAID ONE LEG, MEANS FOR SIMILARLY CONNECTING THE INDIVIDUAL LIGHT SENSITIVE MEMBERS OF ANOTHER PAIR IN THE OTHER DIAGONALLY OPPOSITE LEGS OF THE BRIDGE SO THAT THERE ARE LIGHT-SENSITIVE MEMBERS IN ALL FOUR LEGS OF THE BRIDGE, SAID PAIRS BEING PHYSICALLY POSITIONED FOR RECEIVING SUBSTANTIALLY EQUAL LIGHT ENERGY FROM SAID LIGHT SOURCE WHEREBY THE BRIDGE REMAINS BALANCED FOR VARIATIONS OF BOTH THE VOLTAGE AND LIGHT SOURCE AND IS UNBALANCED BY INTERRUPTION OF THE LIGHT INTENSITY AT ONE PAIR.