also, keep in mind that true 802.3af injectors first put about 10V on
the line to test if the receiving circuit is actually an 802.3af
device and after a period of time either send the 48V or just turn the
psu off.

hjf

On Fri, 4 Feb 2005 17:45:04 -0600, Adi Linden <adil@adis.on.ca> wrote:
> > I was under the impression that to insert POE you would just put some DC
> > on the line, no magnetics needed? (because both ends are already isolated)
> 
> One possible solution is to apply power to the two spare pairs of the
> ethernet run. In that case no magnetics are required. My problem is that I
> have a 802.3af compliant switch. It applies power to the signal pairs.
> Looks like the Linear LTC4257 (and a few other parts) is all I need to use
> the power supplied by the 802.3af switch at the far end. Digi-Key has what
> I need except for magnetics. I guess my original statement was slightly
> wrong in that I am not inserting power but utilizing the available power.
> Not sure what the opposite end of the power inserter would be, power
> remover?
> 
> Adi
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