Installing and Administering PPP

Appendix A 147
Modem Connections
RS-232 Interface
DB-9 to DB-25 Conversion
This wiring diagram shows the standard conversion from DB-9 to DB-25:
Pin Signal Signal Direction
1 Carrier Detect (CD) from DCE
2 Receive Data (RD) from DCE
3 Transmit Data (TD) from DTE
4 Data Terminal Ready (DTR) from DTE
5 Signal Ground both
6 Data Set Ready (DSR) from DCE
7 Request To Send (RTS) from DTE
8 Clear To Send (CTS) from DCE
9 Ring Indicator (RI) from DCE
Pin DB-9 Pin DB-25 Pin
Carrier Detect (CD) 1 8
Receive Data (RD) 2 3
Transmit Data (TD) 3 2
Data Terminal Ready (DTR) 4 20
Ground 5 7
Data Set Ready (DSR) 6 6
Request To Send (RTS) 7 4
Clear To Send (CTS) 8 5
Ring Indicator (RI) 9 22