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Power Over Ethernet Interoperability Guide by Sanjaya Maniktala

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Resistance Imbalance
Suppose we have two resistors: one is 10 Ω, the other is 10 Ω × 1.03 Ω = 10.3 Ω. So it seems natural to intuitively opine that the resistance imbalance is 3 percent (because that’s how we got the factor 1.03). But this statement is not true always, certainly not in PoE. There are actually two ways of expressing resistance imbalance. One is as per the TIA-568B wiring standard mentioned in Chap. 2, which itself is based on the standard ASTM D4566. (ASTM stands for American Society for Testing and Materials.) So this is basically the American way of expressing resistance imbalance (or unbalance):
image
This coincides with our intuitive ...

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