Patent ID: 6860881

Claim:
A return pad contact detection system for use with at least two pairs of patient return pads adapted for contacting a patient, each pair of said at least two pairs of patient return pads having two conductors attached to a corresponding patient return pad for connecting the pad to a source of a.c. energy passing through the pad, said return pad contact detection system comprising: at least two signal sources for generating an operating current for a corresponding pair of said at least two pairs of patient return pads; means for applying the operating current through said conductors to said at least two pairs of patient return pads; and at least two resonant circuits each corresponding to at least one pair of patient return pads and one of said at least two signal sources, each of said at least two resonant circuits responsive to said current for producing a signal which is a function of the impedance between said two corresponding patient return pads, said at least two resonant circuits being tuned to different frequencies and being tuned to substantially the same frequency as the corresponding signal source for substantially minimizing measurement interaction between the at least two pairs of patient return pads when said operating currents are simultaneously applied to said corresponding pairs of patient return pads.