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RE: Here's a new idea:

Hi James,

It occurs to me that the detection method is irrelevant to 
1000BASE-T operation as the link will not be up at the time
of operation. However, the issue at hand is whether you can
inject power at a mid-span in a way that is compatible with
1000BASE-T signalling requirements.

There have been some votes on this subject and my recollection
is certainly not the best thing to rely upon, but I recall 
that 10/100T is a MUST while 1000BASE-T is a WANT.

Using pins 4,5 and 7,8 minimize the potential impact on 10/100T
but would likely have an impact on 1000BASE-T.

There are studies underway to understand just how much these
impacts are and whether they will exclude 1000BASE-T operation.


Dan Dove
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-----Original Message-----
From: James M. Polk [mailto:jmpolk@xxxxxxxxx]
Sent: Monday, May 01, 2000 10:11 AM
To: Bob Bell; tal@xxxxxxxxxxxxxx; stds-802-3-pwrviamdi@xxxxxxxx
Subject: Re: Here's a new idea:


It's Monday, so forgive this clarification, but are you asking Tal to test
his scheme on the signaling pairs of a 10/100BASE connection as well as pins
4/5/7/8 on a 1000BASE-T connection? If not, I'd be curious if Tal could do
this; if so.... then I'm being redundant again redundant again......

At 10:18 AM 5/1/2000 -0600, Bob Bell wrote:
>Tal -
>One of the objectives the group stated was to test for powerablity on the 
>same wires as the power would be provided. In addition, it is desirable 
>that the powering and thus the testing be done in such a manner that the 
>signal carrying capability of the wire pairs not be compromised (this it to

>allow it to work with 1000BaseT. Could your scheme meet these two
>Bob Bell
>At 02:27  4/30/2000, Tal Weiss wrote:
>>Hi all,
>>Since this is my first contribution to the forum and I'm not sure that
>>email forwarding system works, I'll be brief.
>>I read the different discovery process approaches and I want to offer
>>something completely different!
>>All of the proposals in the forum are analog by nature, and lack in
>>I was able to construct a digital "power-identity-chip", costing less than
>>1$, to be implemented inside the powered-IP-phone. This was done using
>>off-the-shelf parts.
>>The chip is powered remotely from the switch using 5 Volts (a simple 5K
>>pull-up resistor does the trick).
>>The power-enabled-switch polls the line for "power-identity-chip" (this
>>be done across wires 4,5 or 7,8) and when a phone is attached the chip is
>>found (CRC protected communication, of course).
>>This chip then tells the switch what it's power requirements are!
>>which wires, power, MAC address and so on...)
>>The power-enabled-switch then applies the correct power using the correct
>>This approach has been tested in the lab and works using different cabling
>>schemes from more than 200 meters!
>>No false alarms and no misses.
>>I know this is different than all the other approaches mentioned above,
>>it works so well I couldn't resist sharing.
>>If more information is needed I'll be glad to supply it!
>>Tal Weiss
>>Congruency Ltd.
>>23 Hasivim St.
>>POB 7813
>>Petah-Tikva 49170, Israel
>>Email:  tal@xxxxxxxxxxxxxx
>>Phone:  972-3-9212322-218
>>Fax  :  972-3-9210757
>Bob Bell
>Cisco Systems Inc.

"At the end of the day... the most committed win!"

James M. Polk
Sr. Product Manager, Multiservice Architecture and Standards
Enterprise Voice Business Unit
Cisco Systems
Dallas, Texas
w) 972.813.5208
f)  972.813.5280