[asterisk-users] Cisco power injector with GXP2000 phones

[Karsten Wemheuer]

Hi,

Am Donnerstag, den 06.12.2007, 11:30 -0500 schrieb Jon Pounder:
> Quoting Ricardo Carvalho <rjcarvalho.lists at gmail.com>:
> 
> > I only see one explanation to my problem...
> >
> > GXP2000 phones only implement PoE mode A of the IEEE 802.3af protocol, and
> > the power injector does only PoE mode B of the IEEE 802.3af protocol. The
> > switch does mode A.
> > The problem is that I can't prove this! can't find documentation with this
> > kind of detail. If someone does, please tell.
> 
> 
> what is the difference between the modes - is it just the pins used ?

Mode A means "inline power". The 48 V is transferred over the wire-pairs
1/2 and 3/6 which are also used for data transfer. Before the power is
switched on, endpoint and power supply must negotiate this process.

Mode B means "midspan power". The 48 V is transferred over the
wire-pairs 4/5 and 7/8, which are unused and 10/100 networks. Mode B is
not possible on GigE (afaik).

Regards,
Karsten