Appendix E

Some Fundamentals of RS-232

RS-232 is a serial interface using DB25 or DB9 connectors and, in some cases, RJ45 connectors. RS-232 specifies both the electrical and mechanical interfaces.

RS-232 is an EIA/TIA norm that is equivalent to V.24/V.28 of the CCITT. V.24, however, specifies the mechanical interface and V.28 the electrical. Both (RS-232, V24/V28) define the same interface and will hereafter be referred to as RS-232.

RS-232 defines the cable connecting a DTE (data terminal equipment—intelligent to data) and a DCE (data communication equipment—pass-through device) and specifies the connector. It is a single-ended interface with one lead for every signal and a ground reference.

The DB25 specification, which is officially called ...

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