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For a straight cable - like from a HUB to a PC, the wires match one for one. To connect two hubs - use a crossover cable.

To Direct Connect two PC's directly to each other use a cross over cable. For the chart beside use the same pin outs on both ends for a straight through cable and different pin outs on each end for a cross over cable.

Cable Wiring Pin Outs

Pin	Color Code for Straight Cable	Color Code for Cross Over Cable
1	White/Green	White/Orange
2	Green	Orange
3	White/Orange	White/Green
4	Blue (voice)	Blue
5	White/Blue (voice)	White/Blue
6	Orange	Green
7	White/Brown (not used)	White/Brown
8	Brown (not used)	Brown

TIA 568B connector to the left is an RJ 45 type. The photo is taken looking at the bottom where the pins are exposed. Note the color coding of the wires from the top down.

As you can see from the 10/100Base-T RJ 45 chart only 4 wires (2 pair) or pins (1, 2, 3 & 6) are being used. Because there are 8 conductors in a cable it is entirely possible and more economical to run two computers on the same cable as long as the wall data jacks are side by side.

For residential telephone wiring the jack to the right only 2 pins or 1 blue pair is being used. Notice that the colour of pairs is different than the above RJ 45 and that the used pins are also different. Also notice how the colours match with the chart

Telephone Rollover Cable Schematic

You can identify a telephone rollover cable by comparing the two connectors at each end of the cable. Hold the cable ends side-by-side, looking at the bottom where the pins are exposed The wire connected to the pin on the outside of the left connector should be the same color as the wire connected to the pin on the outside of the right connector. Telephone rollover cables are not 10Base-T cross over cables. Refer to the above chart for 10/100 Base-T Cross over Cables.