Condition sensing systems and circuits therefor

Claim 1

AN ELECTRICAL CIRCUIT COMPRISING: (A) A PAIR OF TERMINAL POINTS FOR CONNECTION ACROSS A UNIDIRECTIONAL ELECTRICAL POWER SOURCE; (B) FIRST, SECOND, THIRD, AND FOURTH TRANSISTORS, THE FIRST AND THIRD BEING OF ONE TTYPE OF CONDUCTIVITY AND THE SECOND AND FOURTH BEING OF OPPOSITE TYPE OF CONDUCTIVITY; (C) AN INPUT CIRCUIT EXTENDING FROM ONE OF SAID TERMINAL POINTS TO THE OTHER OF SAID TERMINAL POINTS AND INCLUDING A CONNECTION TO THE BASE OF SAID FIRST TRANSISTOR AND INPUT TERMINALS FOR CONNECTION TO AN ELECTRICAL SOURCE POLARIZED TO RENDER SAID FIRST TRANSISTOR CONDUCTIVE; (D) FIRST AND SECOND RESISTORS, (E) AN OUTPUT CIRCUIT COMPRISING THE EMITTER TO COLLECTOR CIRCUIT OF SAID FOURTH TRANSISTOR, SAID FIRST RESISTOR CONNECTED ON THE EMITTER SIDE OF SAID OUTPUT CIRCUIT INTERMEDIATE SAID EMITTER SIDE OF SAID OUTPUT MINAL POINT AND SAID SECOND RESISTOR CONNECTED ON THE COLLECTOR SIDE OF SAID OUTPUT CIRCUIT INTERMEDIATE SAID COLLECTOR AND THE OTHER OF SAID TERMINAL POINTS; (F) SAID FIRST, SECOND, AND THIRD TRANSISTORS HAVING THEIR COLLECTORS CONNECTED TO THE BASES OF SAID SECOND, THIRD, AND FOURTH TRANSISTORS, RESPECTIVELY, THE EMITTER OF SAID SECOND TRANSISTOR BEING CONNECTED TO SAID ONE TERMINAL POINT, AND THE EMITTER OF SAID FIRST AND THIRD TRANSISTORS EACH BEING CONNECTED TO A POINT IN SAID COLLECTOR SIDE OF SAID OUTPUT CIRCUIT.