Modem Cable Pinout - AllPinouts
From AllPinouts
serial interface cable This cable should be used for DTE to DCE (for instance computer to modem) connections with hardware handshaking.

9 pin D-SUB female connector to the Computer

25 pin D-SUB male connector to the modem
Contents |
Modem DSUB9 to DSUB25 cable
| Female | Male | Dir | |
|---|---|---|---|
| Shield | 1 | - | |
| Transmit Data | 3 | 2 | OUT |
| Receive Data | 2 | 3 | IN |
| Request to Send | 7 | 4 | OUT |
| Clear to Send | 8 | 5 | IN |
| Data Set Ready | 6 | 6 | IN |
| System Ground | 5 | 7 | - |
| Carrier Detect | 1 | 8 | IN |
| Data Terminal Ready | 4 | 20 | OUT |
| Ring Indicator | 9 | 22 | IN |
Modem DSUB25 to DSUB25 cable
| Female | Male | Dir | |
|---|---|---|---|
| Shield Ground | 1 | 1 | - |
| Transmit Data | 2 | 2 | OUT |
| Receive Data | 3 | 3 | IN |
| Request to Send | 4 | 4 | OUT |
| Clear to Send | 5 | 5 | IN |
| Data Set Ready | 6 | 6 | IN |
| System Ground | 7 | 7 | - |
| Carrier Detect | 8 | 8 | IN |
| Data Terminal Ready | 20 | 20 | OUT |
| Ring Indicator | 22 | 22 | IN |