RS-232 serial pinouts

25 pin

1 - Ground

2 - Transmit Data (TD)

3 - Receive Data (RD)

4 - Request to send

5 - Clear To Send (CTS)

6 - Dataset ready

7 - Signal Ground (SG)

8 - Data Carrier Detect (DCD)

20 - Data Terminal Ready (DTR)

22 - Ring Indicator

9 pin

1 - Data Carrier Detect (DCD)

2 - Receive Data (RD)

3 - Transmit Data (TD)

4 - Data Terminal Ready (DTR)

5 - Ground

6 - Data set ready

7 - Request to send

8 - Clear To Send (CTS)

9 - Ring Indicator