balanced signal

Balanced signal is any signal in which the two conductors are isolated from ground, and 180 degrees out of phase with each other. Originally developed by the telephone industry, it allows audio signals to be run long distances without noticeable degradation. Balanced lines are used with both microphone and +4 dBm (Line level) signals. The advantage of balanced lines is common mode rejection. Any interference coming into the balanced line is impressed equally on both conductors in phase. Since the desired signal on the lines is 180 degrees out of phase, the interference signal cancels itself out in the input section of the receiving electronics.