Electrical resistance tester

Claim 1

A CIRCUIT FOR INDICATING THE VALVE OF AN ELECTRICAL RESISTANCE COMPRISING (A) A FIRST TRANSISTOR HAVING INPUT AND OUTPUT ELECTRODES, SAID INPUT ELECTRODES OF SAID FIRST TRANSISTOR CONNECTED DIRECTLY ACROSS ELECTRICAL RESISTANCE, (B) A SECOND TRANSISTOR HAVING INPUT AND OUTPUT ELECTRODES, AN INPUT ELECTRODE OF SAID SECOND TRANSISTOR CONNECTED TO AN OUTPUT ELECTRODE OF SAID FIRST TRANSISTOR, AND AN OTHER INPUT ELECTRODE OF SAID SECOND TRANSISTOR CONNECTED TO SAID ELECTRICAL RESISTANCE TO FORM A NEGATIVE FEEDBACK LOOP COMPRISED OF SAID FIRST TRANSISTOR, SAID SECOND TRANSISTOR AND SAID ELECTRICAL RESISTANCE, (C) A RESISTOR, (D) AN INCANDESCENT LAMP, SAID RESISTOR CONNECTED TO THE SAID OUTPUT ELECTRODE OF SAID FIRST TRANSISTOR, AND TO THE OUTPUT ELECTRODE OF SAID SECOND TRANSISTOR, THEREBY TO BE INCLUDED WITHIN SAID FEEDBACK LOOP, (E) MEANS TO POWER SAID CIRCUIT CONNECTED TO SAID ELECTRICAL RESISTANCE AND TO SAID RESISTOR TO ALLOW CURRENT TO FLOW THROUGH BOTH UNDER THE CONTROL OF SAID FIRST AND SECOND TRANSISTORS, AND SAID LAMP CONNECTED IN SAID FEEDBACK LOOP WITH ONE TERMINAL OF SAID LAMP DIRECTLY CONNECTED TO AN ELECTRODE OF SAID SECOND TRANSISTOR, SAID CIRCUIT THUS CONSTITUTED TO INDICATE THE VALUE OF AN ELECTRICAL RESISTANCE BY PROVIDING AN INDICATION BY NON-ILLUMINATION OF SAID LAMP FOR VALUES OF SAID ELECTRICAL RESISTANCE GREATER THAN THE ORDER OF ONE OHM, AND BY PROVIDING AN INDICATION BY ILLUMINATION OF SAID LAMP FOR VALUES OF SAID ELECTRICAL RESISTANCE LESS THAN THE ORDER OF ONE OHM, THE CURRENT THROUGH SAID ELECTRICAL RESISTANCE LIMITED BY THE RESISTANCE OF SAID LAMP, AND THE VOLTAGE ACROSS SAID ELECTRICAL RESISTANCE LIMITED BY THE FORWARD VOLTAGE DROP OF THE TRANSISTOR JUNCTION OF SAID INPUT ELECTRODES OF SAID FIRST TRANSISTOR.