> 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.

Yes, that's how the whole things started. I am trying to power Cisco ip
phones from a Netgear FS108P switch. The switch has four 802.3af compiant
power source ports. After reading about 802.3af I thought that this was
going to be easy - make an adapter that swaps the spare ethernet pairs to
match 802.3af polarity with Cisco legacy polarity, and add a 25.5k
resistor across the power sourcing wires to fool the switch into believing
that a compliant 802.3af device is connected. No go. The timing and
probing of 802.3af is a bit more complex.

The Linear LTC4257 appears to be the proper device to extract power from
an 802.3af source. Unfortunatley, out of the box the FS108P switch does
not power the spare pairs of the ethernet wire. Therefore I am trying to
come up with a solution that properly splits the 802.3af powered data
pairs into data (no power) and power.

I found a few magnetics and RJ45 jacks with integrated magnetics that are
designed for POE. Unfortunately, like so many times in the past, I cannot
seem to find anyone willing to sell these at a reasonable cost in small
quantities.

Adi
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