Patent ID: 7372369

Claim:
A system comprising: an electrical network having at least first and second conductors where the conductors are terminated by a variable impedance, electrically alterable, element; a first current source that produces a first relatively low supervisory test current through the first and second conductors and variable impedance element; a first processor that determines a circuit resistance to the first test current through the first and second conductors and variable impedance element and that detects a short circuit fault type when the determined circuit resistance is less than a predetermined value; a second current source that produces a second supervisory test current through the first and second conductors and the variable impedance element where the second test current has a higher relative magnitude than the first test current and where the first and second test currents are applied at different times; and a second processor that determines a circuit resistance to the second test current through the first and second conductors and variable impedance element and that detects an open circuit fault type when the determined circuit resistance is greater than a predetermined value.