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

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

D25 pin D-SUB female to the PC DB25 pin D-SUB female to the PC
DB25 pin D-SUB male to the modem DB25 pin D-SUB male to the modem

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