Patent ID: 7661427

Claim:
A method for substantially removing a common noise signal portion from electrical signals produced by an electrical signal source having a polarity reversal region with a centre, said electrical signals having inverse polarities on opposite sides of the centre, said method comprising: sensing a first electrical signal of a first polarity through a first electrode pair located on one side of the centre; sensing a second electrical signal of a second polarity through a second electrode pair located on the other side of said centre; sensing a third electrical signal through a third electrode pair located between said first electrode pair and said second electrode pair; combining the first and second electrical signals into a combination signal; and combining the combination signal and the third electrical signal into an output signal, wherein said first and second polarities are opposite polarities; combining the first and second electrical signals comprises subtracting one of the first and second electrical signals from the other of said first and second electrical signals to produce a combination signal substantially free from said common noise signal portion; and combining the combination signal with the third electrical signal comprises adding the combination signal and the third electrical signal to produce said output signal still substantially free from said common noise signal portion and thereby substantially prevent output signal loss.