[Asterisk-Users] POE

[Greg Boehnlein]

On Sat, 28 Aug 2004, Michael Welter wrote:

> Greg Boehnlein wrote:
> > On Sat, 28 Aug 2004, Michael Welter wrote:
> > 
> > 
> >>Since the Cisco 79XX phones preceded the PoE standard, they are 
> >>different--polarity is reversed.
> >>
> >>IANAE, but as I understand the PoE devices, there are two types--one 
> >>always applies -48VDC to the brown pair while the other senses (as per 
> >>the PoE spec.) whether the device at the other end requires power.
> >>
> >>I'm not willing to risk a $300 Cisco set, so I'm still using the wall 
> >>wart.  Is anyone providing LAN power to 79XX phones at a reasonable cost?
> > 
> > 
> > Please see:
> > 
> > http://www.voip-info.org/wiki-Cisco+POE
> > 
> > I am using 3Com POE injectors (the Dumb kind) with Cisco 7960s without a 
> > problem. You need a special cable that you can build or, you can buy a 
> > PowerDSine POE injector and get the following (part PD-PS-401-5/CSCS) 
> > which will do the same thing as the cable.
> > 
> 
> To add to my confusion, the wiki page you referenced says the 7960g 
> phones are different from the original 7960.

Not in terms of POE. No 7960 supports the 802.3af POE protocol and instead 
uses a proprietary Cisco protocol.

The cable that is referenced on those pages reverses the polarity of the 
wires, which with a dumb power injector like the 3com will allow you to 
use the Cisco. However, if you get a regular 802.3af injector, that 
actually speaks and respects the protocol, it STILL won't work with a 
Cisco.

I use the following dumb injector with my Cisco cable;
http://www.3com.com/prod/en_UK_EMEA/detail.jsp?tab=features&sku=3CNJPSE

It works.

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