Patent ID: 7486088

Claim:
An apparatus for preventing corrosion of a contact, the apparatus comprising: a detection conducting path connected to the contact; a variable impedance unit connected to the detection conducting path, the variable impedance unit being switchable between (i) a first impedance used for passing a corrosion prevention current into the detection conducting path and (ii) a second impedance through used for passing a current, which is used for detecting a connection state of the contact, into the detection conducting path, the first impedance being lower than the second impedance; and a comparing and switching unit that compares a detected value with a corrosion threshold, compares the detected value with a restoration threshold which is different from the corrosion threshold and switches the variable impedance unit based on comparing results, wherein: the variable impedance unit comprises: an impedance unit having a third impedance, the impedance unit connected to the detection conducting path; and a switching element connected to the detection conducting path in parallel to the impedance unit, the switching element being switchable between (i) a conduction state where terminals of the switching element are conducting and (ii) a non-conduction state where the terminals of the switching element are not conducting, the switching element having a fourth impedance, the third impedance being larger than the fourth impedance.