Null detecting bridge circuit for testing back resistance of a diode

Claim 1

A CIRCUIT FOR DETERMINING THE REVERSE POTENTIAL WHICH WILL CAUSE THE RESISTANCE OF A NON-LINEAR RESISTANCE ELEMENT TO FALL TO A PREDETERMINED VALUE COMPRISING IN COMBINATION A BRIDGE CIRCUIT HAVING TWO BRANCHES ONE OF SAID BRANCHES INCLUDING MEANS FOR CONNECTING IN SERIES THEREWITH A NON-LINEAR RESISTANCE ELEMENT TO BE TESTED, THE OTHER ONE OF SAID BRANCHES INCLUDING A REFERENCE RESISTANCE ELEMENT, EACH OF SAID BRANCHES ALSO INCLUDING A BALANCED RESISTANCE ELEMENT; MEANS FOR GENERATING A UNIDIRECTIONAL REGULARLY INCREASING POTENTIAL, MEANS FOR APPLYING SAID UNIDIRECTIONAL POTENTIAL ACROSS SAID BRIDGE IN A SENSE SO AS TO BACK BIAS THE RESISTANCE ELEMENT UNDER TEST, DETECTOR MEANS FOR GENERATING A HOLD SIGNAL WHEN SAID BRIDGE CIRCUIT IS IN A BALANCED CONDITION, MEANS RESPONSIVE TO SAID HOLD SIGNAL FOR LOCKING SAID POTENTIAL GENERATING MEANS AGAINST FURTHER CHANGE, AND MEANS FOR INDICATING THE FINAL POTENTIAL APPLIED ACROSS SAID BRIDGE CIRCUIT.