RS/EIA/TIA-423 is a standard for serial communications. It defines an unbalanced (single-ended) interface (similar to RS-232), with a single, unidirectional sending driver, and allows for up to 10 receivers (similar to RS-422). It is normally implemented in integrated circuit technology and can also be employed for the interchange of serial binary signals between DTE & DCE. There is no common pinout for RS-423. The BBC Micro computer used a 5-pin DIN connector. DEC used it extensively with a Modified Modular Jack connector. This was sometimes called "DEC-423".
Use of a common ground is one weakness of RS-423 (and RS-232): if devices are far enough apart or on separate power systems, the ground will degrade between them and communications will fail, resulting in a condition that is difficult to trace. In this respect, balanced serial connections such as RS-422 or RS-485 are better, and Ethernet over twisted pair connections are better yet, because of the galvanic isolation provided by the signal transformers.