RS232 DB9 Pinout
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| Pin | Name | Notes/Description | Direction |
|---|---|---|---|
| 1 | DCD | Data Carrier Detect | In |
| 2 | RD | Receive Data (a.k.a RxD, Rx) | In |
| 3 | TD | Transmit Data (a.k.a TxD, Tx) | Out |
| 4 | DTR | Data Terminal Ready | Out |
| 5 | SGND | Ground | N/A |
| 6 | DSR | Data Set Ready | In |
| 7 | RTS | Request To Send | Out |
| 8 | CTS | Clear To Send | In |
| 9 | RI | Ring Indicator | In |
Null Modem Adapter
| Male | Signal | Male | Signal |
|---|---|---|---|
| 2 | RD | 3 | TD |
| 3 | TD | 2 | RD |
| 4 | DTR | 6,1 | DSR, DCD |
| 6,1 | DSR, DCD | 4 | DTR |
| 7 | RTS | 8 | CTS |
| 8 | CTS | 7 | RTS |
| 5 | SGND | 5 | SGND |
| 9 | RI | 9 | RI |
