In 1975 the EIA introduced two new specifications in order to upgrade system capabilities; these are the RS423 interface, which closely resembles RS232C, and the RS422 and RS485 interfaces, both of which allow higher transmission rates. RS232C operates with a single transmitter and single receiver per channel up to about 20 meters. RS423, RS422, and RS485 operate at up to about 1200 meters at higher speeds and support multiple transmitters and receivers in each channel. RS422 and RS485 operate in differential mode using balanced cables.
"RS232C interface." A Dictionary of Computing. . Encyclopedia.com. (August 15, 2018). http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/rs232c-interface
"RS232C interface." A Dictionary of Computing. . Retrieved August 15, 2018 from Encyclopedia.com: http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/rs232c-interface