Steven Critchfield wrote:

so you will need also something that detects the power request
on each port and enables it.


How does a non powered device request power?

As far as I know, it doesn't. The POE source somehow monitors the line (using impedance, etc) to determine if there is anything connected to the pairs used to supply power. Since netcards and net connected equipment are not supposed to use the "power" pairs, this should work in most cases. If the termination just leaves them unconnected the impedance is infinity and power will not be applied. Conversely, if the termination are all grounded, impedance is (near) 0 and power will not be applied. For some range of impedances in between, the far end is assumed to require power and power will be applied.


Stephen R. Besch

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