Source : Free On-Line Dictionary of Computing

differential line
     
         A kind of electrical connection using two wires,
        one of which carries the normal signal (V) and the other
        carries an inverted version the signal (-V).  A differential
        amplifier at the receiver subtracts the inverted signal from
        the normal signal to yield a signal proportional to V.  This
        subtraction is intended to cancel out any noise induced in the
        wires, on the assmption that the same level of noise will have
        been induced in both wires.  {Twisted pair} wiring is often
        used to try to ensure that this is the case.
     
        The two wires might be connected at the receiver to separate
        {analogue to digital converters} and the subtraction performed
        digitally.
     
        The {RS-422} {serial line} {standard} specifies differential
        drivers and receivers, whereas the earlier {RS-232} standard
        does not.
     
        Opposite: {single ended}.
     
        (1995-03-08)