Classification “Gray Areas”
The unspecified regions between the above-mentioned class ranges are “gray areas,” and the PSE is technically allowed to read either of the adjacent classes. It seems more advisable, however, that the PSE should read the class corresponding to higher power, simply to avoid “strange” shutdowns of ports. For example if the PSE reads 23 mA, then as per the standard it is free to interpret the PD as either Class 2 or Class 3. But to avoid an inconvenient port shutdown, a more practical choice seems to be to make the PSE err on the side of higher power.
Prevention is always better than cure. So to avoid this ambiguous situation altogether, the best option is that the PD should itself be well-designed—in particular, its ...
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