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
«—