

Need a null modem cable but aren’t sure of the difference between those and serial cables? Both may use db9 female rs232 so it is easy to confuse the cables. While a null modem adapter may indeed have a db9 f to connect serial devices to a pc via serial port they have a unique pinout which uses a null modem connection. Devices such as an external modem are considered DTE and will use a standard rs 232 cable while Data Communications Equipment, DCE for short are the ones which require a Null Modem Cable.
DB9 to DB9 Null Modem Pinouts |
1 & 6 |
4 |
2 |
3 |
3 |
2 |
4 |
1 & 6 |
5 |
5 |
7 |
8 |
8 |
7 |
|
|
DB9 to DB25 Null Modem Pinouts |
2 |
2 |
3 |
3 |
4 & 5 |
1 |
6 |
4 |
7 |
5 |
8 |
7 & 8 |
20 |
6 |
22 |
9 |
|