Wiring Tutorial for 10BaseT 100BaseTX Unshielded Twisted Pair (UTP)

     The pairs of wires in UTP cable are colored so that you can identify the same wire at each end. Furthermore, they are usually color coded by pair so that the pairs can also be identified from end to end. Typical CAT5 UTP cables contain 4 pairs made up of a solid color and the same solid color striped onto a white background. The most common color scheme is the one that corresponds to the Electronic Industry Association/Telecommunications Industry Association's Standard 568B

Most commonly used standard

Pin # Conductor Color Code 1 white/orange 2 orange 3 white/green 4 blue 5 white/blue 6 green 7 white/brown 8 brown

Pin # Conductor Color Code 1 white/green 2 green 3 white/orange 4 blue 5 white/blue 6 orange 7 white/brown 8 brown

     The cable connectors and jacks that are most commonly used with CAT5 UTP cables are RJ45. The RJ simply means Registered Jack and the 45 designation specifies the pin numbering scheme. The connector is attached to the cable and the jack is the device that the connector plugs into, whether it is in the wall, the network interface card in the computer, or the hub.

The IEEE Specification for Ethernet 10BaseT requires that two twisted pairs be used and that one pair is connected to pins 1 and 2, and that the second pair is connected to pins 3 and 6. Yes that is right - pins 4 and 5 are skipped and are connected to one of the remaining twisted pairs.

wire Pair#2 (white/orange, orange) and Pair#3 (white/green, green) are the only two pairs used for 10BaseT data.

According to the EIA/TIA-568B RJ-45 Wiring Scheme:

Both ends should have the same pin assignments
Pin 1 White/Orange
Pin 2 Orange
Pin 3 White/Green
Pin 4 Blue
Pin 5 White/Blue
Pin 6 Green
Pin 7 White/Brown
Pin 8 Brown

In order to make what is commonly referred to as a "Crossover" cable one must change the pinout connections on ONE end of the cable. If you do it on both ends of the cable you have crossed-over the crossover and now have a straight-through cable, albeit a very non-standard one. In this case two negatives do make a positive.

You need to make a cable where pins 1 & 2 from one end are connected to pins 3 & 6 on the other end, and pins 3 & 6 from the first end are connected to pins 1 & 2 on the other end. Pins 4 & 5 and 7 & 8 are unchanged.

The two ends look like this:

The crossover pairs are illustrated in the following diagram