These last three pages of the following presentation give enough of an
overview to implement it:
http://www.poweroverethernet.com/logscreensizeurl/content/view/full/349/offset/3

The upshot is that the supply tests for a 25k ohm resistance on the
extra pairs, or between the data pairs, and only supplies the 48v if
that resistance exists.  The equipment must draw a minimum of current
(but no greater than 13W).  If the current drops below a threshold (I'd
assume the 25kohm threshold for starters, until you get the real spec)
then the power is disconnected and the discovery process begins again.

Sounds fairly simple and straightforward.  The items you'll be missing
are things like: Must maintain a 1500 isolation, and other such safety
rules.

I hope this helps!

-Adam

Josh Koffman wrote:

>Thanks for the link. I've seen similar ones. While this may work for
>individual users, 802.3af is a standard that specifies how power
>suppliers and power users can co-exist on the network without damaging
>non 802.3af compliant devices. There is a bunch of stuff about sensing
>resistances...or so I gather. That's why I need more data :)
>
>Josh
>--
>A common mistake that people make when trying to design something
>completely foolproof is to underestimate the ingenuity of complete
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>
>"Rick C." wrote:
>
>
>>This might help:
>>http://www.wireless.org.au/~jhecker/poe/
>>
>>
>
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