RS-423
Short for Recommended Standard 423 and sometimes called TIA/EIA-423, RS-423 is a telecommunications specification defined by the EIA (Electronic Industries Alliance). It outlines the electrical characteristics for a balanced voltage, digital interface circuit. Like RS-422, but with unbalanced signaling, RS-423 is utilized in serial communication between DTE (data terminal equipment) and DCE (data communication equipment).
For example, a serial RS-423 signal might transmit from a modem to a dumb terminal over a cable with a D-sub connector.
Although RS-423 was intended to be the successor to RS-232 with its longer cable length of up to 3900 feet (1200 meters), it is not widely used. It should be noted that RS-423 only supports point-to-point connections.