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I would confirm what Keng-hua reports, that I know of many PHYs with the crossover correction, on both sets of pairs independently. I agree that this feature in the PHYs works data-only, and will not effect powering. However, because of this feature, we therefore do not see any trouble calls from mis-connected crossover cabling. Therefore we do not seem to have a good way to see whether the two sets of pairs are crossed over independently in the field.
One reason that the feature is popular is that the equipment vendor no longer has to worry about the configuration of the wiring (with regards to crossovers). Specifying a specific configuration for 4-pair POE applications seems to be a step backwards, and would lead us back to the days when the end-user would have to have multiple sets of patch cords handy when connecting a new link so that he could make sure he had the right crossover combination at the end point. Remember that there are several connections in the link topology where a crossover may or may not occur (either by mistake or by design).
Principal, CME Consulting
Experts in Advanced PHYsical Communications Technology
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