Cable Pinouts

Ethernet

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

Serial

NULL

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

STD (Straight-Through)

DB25 Pin Adapter Color
2 Yellow
3 Green
4 Gray
5 Brown
6 Blue
7 Red
20 Black
Orange

INTEL

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