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-   -   How does "Power-Over-Ethernet" work? (http://www.velocityreviews.com/forums/t234551-how-does-power-over-ethernet-work.html)

Ramon F Herrera 11-18-2005 07:04 PM

How does "Power-Over-Ethernet" work?
 
As we all know, 100BT uses 2 pairs, one for Tx, one for Rx.

One of the reason they were able to squeeze 1GB on Ethernet was by
using all 8 conductors.

So, if I have a Gigabit LAN with VoIP phones, how is the power
delivered to the SIP phones if all conductors are used already?

TIA,

-Ramon


Doug McIntyre 11-18-2005 08:58 PM

Re: How does "Power-Over-Ethernet" work?
 
"Ramon F Herrera" <ramon@conexus.net> writes:
>As we all know, 100BT uses 2 pairs, one for Tx, one for Rx.


>One of the reason they were able to squeeze 1GB on Ethernet was by
>using all 8 conductors.


>So, if I have a Gigabit LAN with VoIP phones, how is the power
>delivered to the SIP phones if all conductors are used already?



The standard specifies several modes, one of which is shared signal
and power, but I haven't seen anybody run in this mode. All I've seen
is power over the unused pins after the two ends negotiate what mode
they'll be in.

Most often, you get 10/100 and PoE connections. Gigabit has to be
handled seperately out to the desktop.





R-Guy 11-19-2005 12:23 AM

Re: How does "Power-Over-Ethernet" work?
 
"Doug McIntyre" <merlyn@geeks.org> wrote in message
news:437e406f$0$30641$892e0abb@auth.newsreader.oct anews.com...
> "Ramon F Herrera" <ramon@conexus.net> writes:
>>As we all know, 100BT uses 2 pairs, one for Tx, one for Rx.

>
>>One of the reason they were able to squeeze 1GB on Ethernet was by
>>using all 8 conductors.

>
>>So, if I have a Gigabit LAN with VoIP phones, how is the power
>>delivered to the SIP phones if all conductors are used already?

>
>
> The standard specifies several modes, one of which is shared signal
> and power, but I haven't seen anybody run in this mode. All I've seen
> is power over the unused pins after the two ends negotiate what mode
> they'll be in.
>
> Most often, you get 10/100 and PoE connections. Gigabit has to be
> handled seperately out to the desktop.
>
>
>
>

This box does POE on 1000base-T according to 802.3af:
http://www.phihong.com/assets/pdf/PSA20U.pdf




Jeff Little 11-19-2005 05:56 AM

Re: How does "Power-Over-Ethernet" work?
 
Evening Ramon;

More info than you probably wanted to know:

http://www.poweroverethernet.com/

Jeff


On 18 Nov 2005 11:04:13 -0800, "Ramon F Herrera" <ramon@conexus.net>
wrote:

>As we all know, 100BT uses 2 pairs, one for Tx, one for Rx.
>
>One of the reason they were able to squeeze 1GB on Ethernet was by
>using all 8 conductors.
>
>So, if I have a Gigabit LAN with VoIP phones, how is the power
>delivered to the SIP phones if all conductors are used already?
>
>TIA,
>
>-Ramon



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