Balanced line

A cable (such as a three-pin XLR mic cable) with two conductors surrounded by a shield in which each conductor is at equal impedance to the ground. With respect to ground, the conductors are at equal potential but opposite polarity. The balanced line reduces noise because as the two conductors pick up noise, the opposing polarity ensures the noise is canceled when the inverted signal on one conductor is 'added' to the original signal on the second conductor after the signal reaches the destination.