Control unit for automatic cathodic protection

Claim 1

IN A CATHODIC PROTECTION SYSTEM MEANS FOR DETECTING CHANGES IN POTENTIAL DIFFERENCE BETWEEN AN OBJECT BEING PROTECTED AND A PROTECTION ANODE IRRESPECTIVE OF ENVIRONMENTAL CONDITIONS OR PREVIOUS REGULATORY CURRENTS EXISTING THEREBETWEEN, COMPRISING: A SOURCE OF POWER; FIRST AND SECOND SOURCES OF DIFFERING STATIC ELECTRICAL POTENTIAL IN WHICH THE SAID OBJECT AND ANODE ARE RESPECTIVELY LOCATED; THRESHOLD GATING MEANS HAVING A FIRST INPUT ELEMENT CONNECTED TO SAID SOURCE OF POWER AND TO SAID FIRST SOURCE OF PONTENTIAL, AND A SECOND INPUT ELEMENT CONNECTED TO SAID SECOND SOURCE OF POTENTIAL; SAID GATING MEANS HAVING A FURTHER ELEMENT WHEREBY A SMALL OPERATING CURRENT NORMALLY FLOWS BETWEEN SAID SECOND AND FURTHER ELEMENTS; MEANS ISOLATING SAID SMALL CURRENT FLOW FROM SAID SOURCES OF POTENTIAL; SAID THRESHOLD GATING MEANS BEING BIASED TO NON-CONDUCTION BETWEEN SAID FIRST AND SECOND INPUT ELEMENTS WHEN THE POTENTIAL DIFFERENCE BETWEEN SAID SOURCES OF POTENTIAL IS AT A PREDETERMINED LEVEL AND BEING BIASED TO CONDUCTION WHEN THE DIFFERNCE IN POTENTIAL BETWEEN SAID SOURCE OF POTENTIAL DECREASES FROM SAID PREDETERMINED LEVEL BY A PREDETERMINED AMOUNT.