[asterisk-users] Cisco power injector with GXP2000 phones

[Jon Pounder]

Quoting Kristian Kielhofner <kristian.kielhofner at gmail.com>:

> On Dec 6, 2007 10:44 AM, Jon Pounder <JonP at inline.net> wrote:
>> Quoting Salvatore Giudice <Salvatore.Giudice at VoIPSecurityTraining.com>:
>>
>> > The electricity is carried on different pins in a cisco poe injector. Just
>> > because they both support the same standard doesn't mean they were
>> > implemented the same.
>> >
>>
>> I didn't even know the gxp2000's could handle poe - anyone care to
>> share what voltage/current they expect on what pins ?
>>
>> even if I could just move the existing powersupplies back to the
>> punchdown panel that would unclutter desks and make centralizing ups
>> power that much simpler.
>>
>
>   Not a good idea.
>
>   The Grandstreams expect 48V just like every other POE device.  Their
> power supplies are 12V.  Simply splicing them inline with an ethernet
> cable won't work.  To boot, some older Grandstreams use 5V power
> supplies.  That obviously won't work either.  48V is nice because it
> is high enough voltage to not suffer distribution loss over cable runs
> but low enough to not cause major harm and still qualify as "low
> voltage" under many codes, laws, etc.
>
>   The biggest problem is that any properly implemented PoE device
> negotiates PoE.  The other pairs of ethernet are not just live,
> supplying 48V DC to anything.  That's why I refuse to use "passive"
> PoE.  Just seems dangerous!

I guess I just live dangerous, I normally wire all rj45s to be phone  
on blue and ethernet on org/green. And guess what's on phone ? the  
same 48Vdc and even more if it happens to ring.

Then if I plug in ethernet it works, or plug in phone it works, and I  
don't have to be too concerned about which jack is which.





>
>
> --
> Kristian Kielhofner
>
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Jon Pounder

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