RS-422 and RS-423 - Hardware
Standard interfaces approved by the Electronic Industries Association (EIA) for connecting serial devices. The RS-422 and RS-423 standards are designed to replace the older RS-232 standard because they support higher data rates and greater immunity to electrical interference. All Apple Macintosh computers contain an RS-422 port that can also be used for RS-232C communication. RS-422 supports multipoint connections whereas RS-423 supports only point-to-point connections.