RS232 Modem Cable Layout (2-wire, DB9-DB25). Pinout and signals for building a two-wire serial (RS232) modem cable
This cable should be used for DTE to DCE (for instance computer
to modem) connections without hardware handshaking.
 |
DB9 pin D-SUB female to the computer |
 |
DB25 pin D-SUB male to the modem |
| |
Female |
Male |
Direction |
| Shield Ground |
|
1 |
|
| Transmit Data |
3 |
2 |
→ |
| Receive Data |
2 |
3 |
← |
| System Ground |
5 |
7 |
|
| Jumper these: |
| Request to Send |
7 |
|
← |
| Clear to Send |
8 |
|
← |
| Data Set Ready |
6 |
|
← |
| Carrier Detect |
1 |
|
← |
| Data Terminal Ready |
4 |
|
→ |
| Request to Send |
|
4 |
→ |
| Clear to Send |
|
5 |
← |
| Data Set Ready |
|
6 |
← |
| Carrier Detect |
|
8 |
← |
| Data Terminal Ready |
|
20 |
→ |