27.1. The RS-232C standard

Most serial ports conform to some variant of the RS-232C standard. This standard specifies the electrical characteristics and meaning of each signal wire, as well as pin assignments on the traditional 25-pin (DB-25) serial connector shown in Exhibit A.

Figure A. A male DB-25 connector


Full RS-232C[1] is overkill for all real-world situations since it defines numerous signals that are unnecessary for basic communication. DB-25 connectors are also inconveniently large. As a result, a number of alternative connectors have come into widespread use. These are described in the section titled Alternative connectors ...

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