Hi Saad,
The problem here is that the 7940 and other older Cisco phones use a pre-standard power and not 802.3af PoE which the 3com uses.
Q. What IP phone models support the Cisco pre-standard method of powered device detection?
A. These Cisco IP phones can accept Cisco pre-standard PoE from a card integrated with a Cisco Catalyst switch or a Catalyst in-line power patch panel:
7985G
7960G
7940G
7910G
7910G + SW
7912G
7905G
7902G
These phones can draw local power from a power cube (CP-PWR-CUBE-2=) in addition to a country or regionally specific power cord (CP-PWR-CORD-xx=).
Q. What IP phone models support the IEEE standard method of powered device detection?
A. These Cisco IP phones support IEEE 802.3af PoE:
7961G-GE
7971G-GE
7941G
7931G
7911G
7941G-GE
Note: These Cisco IP phones support both the Cisco pre-standard PoE and IEEE 802.3af PoE:
7970G
7961G
7906G
From this new doc;
Power over Ethernet (PoE) Power Requirements FAQ
http://www.cisco.com/en/US/products/hw/phones/ps379/products_qanda_item09186a00808996f3.shtml
You probably need a third party product like;
PowerDsine 6000 Power over Ethernet Midspan Family
http://www.powerdsine.com/Products/Midspan/PD_6000.asp
Good chart that shows 7960 etc.
http://www.powerdsine.com/Partners/Cisco/solutions.asp
Hope this helps!
Rob
EDIT: Paolo, please remember my limitations when it comes to typing :) Huff
