The DB9 (originally DE-9) connector is an analog 9-pin plug of the D-Subminiature connector family (D-Sub or Sub-D).
The DB9 connector is mainly used for serial connections, allowing for the asynchronous transmission of data as provided for by standard RS-232 (RS-232C).
Note that there are DB9-DB25 adapters for easily converting a DB9 plug into a DB25, and vice versa.
| Pin number | Name | |
|---|---|---|
| 1 | CD - Carrier Detect | |
| 2 | RXD - Receive Data | |
| 3 | TXD - Transmit Data | |
| 4 | DTR - Data Terminal Ready | |
| 5 | GND - Signal Ground | |
| 6 | DSR - Data Set Ready | |
| 7 | RTS - Request To Send | |
| 8 | CTS - Clear To Send | |
| 9 | RI - Ring Indicator | |
| Shield |
