Here's a new idea:
Since this is my first contribution to the forum and I'm not sure that this
email forwarding system works, I'll be brief.
I read the different discovery process approaches and I want to offer
something completely different!
All of the proposals in the forum are analog by nature, and lack in
I was able to construct a digital "power-identity-chip", costing less than
1$, to be implemented inside the powered-IP-phone. This was done using
The chip is powered remotely from the switch using 5 Volts (a simple 5K
pull-up resistor does the trick).
The power-enabled-switch polls the line for "power-identity-chip" (this can
be done across wires 4,5 or 7,8) and when a phone is attached the chip is
found (CRC protected communication, of course).
This chip then tells the switch what it's power requirements are! (Voltage,
which wires, power, MAC address and so on...)
The power-enabled-switch then applies the correct power using the correct
This approach has been tested in the lab and works using different cabling
schemes from more than 200 meters!
No false alarms and no misses.
I know this is different than all the other approaches mentioned above, but
it works so well I couldn't resist sharing.
If more information is needed I'll be glad to supply it!
23 Hasivim St.
Petah-Tikva 49170, Israel
Fax : 972-3-9210757