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The RS-422 and RS-423 electrical standards replaced the RS-232 standard. RS-422 applies to digital signaling circuits that use multipoint connections. RS-423 applies to serial communications with point-to-point connections.
RS-422 was designed for the direct connection of intelligent devices, whereas RS-423 was designed to enhance RS-232 and as a RS-422 and RS-232 intermediary. Both standards are approved by the Electronic Industries Alliance (EIA).
The RS-422 and RS-423 standards are designed to support higher data transfer rates (DTR) with greater interference resistance. All Apple Macintosh computers contain an RS-422 port that may be used for RS-232C communications.
RS-422 provides DTR support up to 10 Mbps and cable lengths up to 4,000 feet. RS-422 converters may be used to extend the range of RS-232 connections. RS-423 provides DTR support up to 100 Kbps and cable lengths up to 4,000 feet. RS-423 supports only one unidirectional driver with up to 10 receiving devices.
RS-423 and RS-232 share the disadvantage of all devices that use common ground, which degrades device communication and can result in potential communication failure where cause is often indeterminable. In this respect, RS-422, RS-485 and Ethernet over twisted pair connects are superior.