RS-232 pin assignment

9-pin connector 25-pin connector Shortcut Pin description
3 2 TxD Transmit Data
2 3 RxD Receive Data
5 7 GND Signal Ground
4 20 DTR Data Terminal Ready
6 6 DSR Data Set Ready
1 8 DCD Data Carrier Detect
7 4 RTS Request To Send
8 5 CTS Clear To Send
9 22 RI Ring Indicator