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Spare pair termination.




Terry, Sterling, Alan, et al.

I have questions concerning high frequency termination, especially the
spare pairs.

How should the spare pairs be terminated in the PD and PSE?

Or more specifically:
    What termination is needed for pairs 4&5 and 7&8?
        Differential:
            Is a differential termination required for these pairs?
            Can they be shorted?
        Common mode:
            Is a common mode termination to ground(?) required?
        Pair to pair mode:
            Is a pair to pair termination required?

If a PD can accept power from signal pairs and spare pairs, is isolation
required.

If a PSE is designed for Environment A, is isolation required between
ports?

Please excuse my ignorance.  If you think this is inappropriate, please
state so.

Dieter Knollman