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

This cable should be used for DTE to DCE (for instance computer to modem) connections with hardware handshaking.

DB9 pin D-SUB female to the PC DB9 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 1
Transmit Data 3 2
Receive Data 2 3
Request to Send 7 4
Clear to Send 8 5
Data Set Ready 6 6
System Ground 5 7
Carrier Detect 1 8
Data Terminal Ready 4 20
Ring Indicator 9 22