Serial (RS232) modem cable (DB9-DB25). Pinout and signals for building a Two-Wire serial (RS232) modem cable

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

DB9 pin D-SUB female to the computer DB9 pin D-SUB female to the computer
DB25 pin D-SUB male to the modem DB25 pin D-SUB male to the modem

  Female Male Direction
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