Two-Wire modem (9-25) cable

pinout

This cable should be used for DTE to DCE (for instance computer to modem) connections without hardware handshaking.

9 pin D-SUB female connector  to the Computer

Female Male Dir Shield Ground   1   Transmit Data 3 2 Receive Data 2 3 System Ground 5 7           Jumper these:       Request to Send 7   Clear to Send 8           Data Set Ready 6   Carrier Detect 1   Data Terminal Ready 4           Request to Send   4 Clear to Send   5         Data Set Ready   6 Carrier Detect   8 Data Terminal Ready   20

25 pin D-SUB male connector  to the Modem

Source:www.pinouts.ru