Source : Free On-Line Dictionary of Computing

EIA-422
     
         (Formerly "RS-422") An {EIA}
        {serial line} {standard} which specifies 4-wire,
        {full-duplex}, {differential line}, {multi-drop}
        communications.  The mechanical connections for this interface
        are specified by {EIA-449}.  The maximum cable length is
        1200m.  Maximum data rates are 10Mbps at 1.2m or 100Kbps at
        1200m.  EIA-422 cannot implement a truly multi-point
        communications network (such as with {EIA-485}), although only
        one driver can be connected to up to ten receivers.  The best
        use of EIA-422 is probably in {EIA-232} extension cords.
     
        {Comparing EIA-422, 423, 449 to RS-232-C
        (http://www.rad.com/networks/1995/rs232/rs449.htm)}.  {Details
        on RS-232, 422, 423 and 485
        (http://www.rs485.com/rs485spec.html)}.
     
        (2002-10-05)