If you buy an ethernet patch cable, it always has the 568-B wiring pattern on both ends. If you buy an ethernet crossover cable, it has the 568-A wiring pattern on one end and the 568-B wiring pattern on the other end.
I have never seen a structured cabling installation for data that didn't use the 568-B wiring pattern. Cabling that was installed for an Avaya Merlin, Legend, Partner or similar phone system typically uses the 568-A wiring pattern.
There is a subtle difference between the two wiring patterns that makes little or no practical difference. The four twisted cable pairs in a standard Cat 5 cable each has a different twist rate. So they are of slightly different lengths. The more twists per inch, the longer the actual conductor. Isn't that right, ED?
