The house ethernet standard is T568B:
| RJ45 Pin | Color | Pair |
|---|---|---|
| 1 | White/orange | 2 |
| 2 | Orange | 2 |
| 3 | White/Green | 3 |
| 4 | Blue | 1 |
| 5 | White/Blue | 1 |
| 6 | Green | 3 |
| 7 | White/Brown | 4 |
| 8 | Brown | 4 |
This mapping is the same for male and female connectors.
| DB9 Pin | DTE Function | Adapter Color | RJ45 Pin |
|---|---|---|---|
| 1 | CD | ||
| 2 | Rx | Yellow | 6 |
| 3 | Tx | Green | 5 |
| 4 | DTR | Blue | 1 |
| 5 | GND | Red | 4 |
| 6 | DSR | Black | 3 |
| 7 | RTS | Brown | 7 |
| 8 | CTS | Gray | 8 |
| 9 | RI | ||
| Orange | 2 |
| DB25 Pin | PM Function | Adapter Color | RJ45 Pin |
|---|---|---|---|
| 2 | Tx | Green | 5 |
| 3 | Rx | Yellow | 6 |
| 4 | RTS | Brown | 7 |
| 5 | CTS | Gray | 8 |
| 6 | DSR | Black | 3 |
| 7 | GND | Red | 4 |
| 20 | DTR | Blue | 1 |
| Orange | 2 |
| DB25 Pin | Adapter Color |
|---|---|
| 2 | Yellow |
| 3 | Green |
| 4 | Gray |
| 5 | Brown |
| 6 | Blue |
| 7 | Red |
| 20 | Black |
| Orange |
There are two standards for IDC-to-DB9, one is the standard straight-through method, mapping pin n on the IDC to pin n on the DB-9. The other is “Intel” format, which does a completely daft mapping. This is explained here.
You can detect this by measuring the voltage between pin 5 and pins 2 and 3, one of which should be positive and one negative. In the Intel configuration, pin 5 isn't ground, and the voltage on pins 2 and 3 will have the same sign.
| DB9 Pin | Color |
|---|---|
| 1 | |
| 2 | Green |
| 3 | Red |
| 4 | Brown |
| 5 | |
| 6 | Yellow |
| 7 | Blue |
| 8 | Black |
| 9 | Gray |