DB-9F DB-25M Function.
1 8 Data Carrier Detect (DCD).
2 3 Receive Data (RD or Rx).
3 2 Transmit Data (TD or Tx).
4 20 Data Terminal Ready (DTR).
5 7 Signal Ground (SGND or Gnd).
6 6 Data Set Read (DSR).
7 4 Request To Send (RTS).
8 5 Clear To Send (CTS).
9 22 Ring Indicator (RI).