Serial (RS232) modem cable (DB9-DB15)
This cable connects an internal modem or terminal adapter that brings its RS232 lines out on a 15-pin socket (the Speedster 14.4 series was a common example) to the 9-pin port of a computer. The 15-pin side is not a standard: check the pinout of your device against this table before wiring it.
The 9-pin side follows the standard DB9 pinout of the PC. The 15-pin side is specific to this modem: the DB15 serial pinout page covers X.21, the usual meaning of a 15-pin serial connector, the RS232 connector pinouts page compares DB9, DB15, DB25 and RJ45, and the full signal set is on the 25-pin RS232 port pinout.
 | DB9 pin D-SUB female to the PC |
 | DB15 pin D-SUB female to the modem |
| 9 pin | 15 pin | Direction | |
|---|---|---|---|
| Carrier Detect | 1 | 11 | ← |
| Receive Data | 2 | 13 | ← |
| Transmit Data | 3 | 12 | → |
| Data Terminal Ready | 4 | 10 | → |
| System Ground | 5 | 1+8+15 | |
| Data Set Ready | 6 | 3 | ← |
| Request to Send | 7 | 4 | → |
| Clear to Send | 8 | 5 | ← |
| Ring Indicator | 9 | 6 | ← |
Null modem (crossed) cable DB9 connectors
Null modem (crossed) cable DB9 and DB25 connectors
Null modem (crossed) cable DB25 connectors
Modem (straight) cable (DB9-DB25)
Modem (straight) cable (DB25-DB25)