Female & male SUB – D 9 Serial Pin Connector

The DE-9 D-sub 9-pin connector is often mistakenly referred to as the "DB-9" connector.  The "E" refers to the shell size.  A "DB-25" connector has a "B" size shell, but the common nine-pin connector is smaller and has an "E" size shell.

            

This  connector (regardless what you call it) is used for a variety of purposes.  Two common applications are RS-232/EIA-232 (serial) connections (including UPS cables), and a variety of video interfaces on the IBM PC.  

Here's a good set of figures for D-sub 9 male and female connectors, as viewed from the pin side (not the solder side):

Refer at the Table 1, this is table of pins commanly used for RS-232 (Serial):

Table 1: RS-232 Serial Connection

Figure: Male SUB – D 9 pin connector and Serial cable.