[Asterisk-biz] PoE for Cisco Phones

[Kevin P. Fleming]

Adi Linden wrote:

> I have 4 Cisco phones (7905G and 7940) that I would like to power from the
> same UPS as the Asterisk server. This requires PoE. I purchased a Netgear
> FS108P, a 8-port ethernet switch with 4 802.3af power ports. Unfortunately
> I haven't been able to convince it to provide power to a Cisco phone by
> just building a simple passive adapter.

As you have discovered, this will not work. The reason it does not work 
is that the Cisco phones do not implement the 802.3af negotiation 
protocol, so the switch does not think there is any need to put power on 
the cable.

> So now I am looking for alternatives. Anything out there that converts
> 802.3af power to power for Cisco phones? Anythings else that provided
> Cisco style POE for a small number of phones? And no, I am not interested
> in a solution that costs more than the phones did, my aim is $25 per
> phone to provide power...

We use 3Com NJPSE (or the generic Ault equivalent), which is a dumb 
power injector, along with the cross-over adapter cable which is 
documented on the wiki. The 3Com units are generally available for under 
$25... we have bought some of the generic ones for under $20.