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Fwd: RE: detecting a PD disconnection event


I may have picked on Jerry unfairly in my note attached below.
This note is intended to pick on everybody.

Please confine the discussions on this reflector to technical issues, NOT to whether or not something will function as a patent work-around.

Avoidance of this area should be taken as seriously as avoidance of discussions of cost.

Now that having been said, lets have a vigorous discussion of the technical merits of a new approach.

We all know why a new approach is being discussed and nothing more needs to be said about that.

Thank you.

Geoff Thompson, Chair, IEEE 802.3

Date: Mon, 30 Apr 2001 13:41:30 -0700
To: "Bachand, Jerry" <gbachand@xxxxxxxxx>
From: "Geoff Thompson" <gthompso@xxxxxxxxxxxxxxxxxx>
Subject: RE: detecting a PD disconnection event
Cc: stds-802-3-pwrviamdi@xxxxxxxx


As I said to you in my private note.
Your discussion below is a legal one, not a technical one.

The judgement of the technical members of P802.3af, who are not expected to be legal experts, are not particularly relevant to whether or not a court would find that there had or had not been infringement.

You should have that discussion with your own legal staff, not here.

If you choose to continue your support for a particular approach based on your opinion that it would not infringe then go ahead.

If you choose to change your vote for a particular approach based on your opinion that an earlier proposal would infringe then go ahead.

Either way, please do not use this forum discuss the matter of whether or not an implementation would infringe. A discussion of that sort is a legal matter, not a technical matter.

As I said in my original message, if you have questions or issues with this them please take up with me directly and DO NOT copy the list.


At 03:40 PM 4/30/01 -0400, Bachand, Jerry wrote:

Their application is for theft prevention/security.
I didn't see in the patent, any mention of using the current drop to
control/turn off power, I'm still looking though.

Since we are not involved in network security, as the patent title states,
the patent shouldn't prevent any one from using a series loop current drop
to detect the need to turn off power to a circuit.

Note:  The title of the patent is:
Network Security System For Detecting Removal Of Electronic Equipment.

If we stay out of the security business, we may be OK.


        Gerard E. (Jerry) Bachand
Avaya Inc.
300 Baker Avenue, Suite 100
Concord, MA 01742

(978) 318-6402  Voice
(978) 318-6402  Fax


        Formerly: Enterprise Networks Group
 ("Cajun" LAN Systems)
of Lucent Technologies

-----Original Message-----
From: Paul Moore [mailto:pamoore@xxxxxxxxxxxxxxxxxx]
Sent: Monday, April 30, 2001 12:05 PM
To: Bachand, Jerry
Cc: Rick Brooks; Barry Male; stds-802-3-pwrviamdi@xxxxxxxx
Subject: RE: detecting a PD disconnection event

I believe the claims in the patent are very specific (that's probably why it
was granted).  It is for sensing  loss of current on a networking cable to
see if something has been disconnected.  Unfortunately this is the very
specific case we are working with, so it seem alternative solutions would be

At 12:06 PM 4/27/2001, Bachand, Jerry wrote:

Rick and group,

I still prefer 1a.
Since detecting a minimum current is such a basic and obvious means to
detect a disconnect, I don't think anyone could even think of suing.  (Not
even Lucent or Avaya.)  ;-)

This means of detecting a disconnect has been in use for over 100yrs by
telephone companies, worldwide, to detect the telephone on-hook condition.

However, I have no problem with other means, as you mentioned, as long as
the minimum current method can still be used.

Please keep in mind, eventually there will be many other devices powered by
the Ethernet, simple might give us more flexibility in the future.



        Gerard E. (Jerry) Bachand
Avaya Inc.
300 Baker Avenue, Suite 100
Concord, MA 01742

(978) 318-6402  Voice
(978) 318-6402  Fax


        Formerly: Enterprise Networks Group
 ("Cajun" LAN Systems)
of Lucent Technologies

-----Original Message-----
From: Rick Brooks [ mailto:ribrooks@xxxxxxxxxxxxxxxxxx
<mailto:ribrooks@xxxxxxxxxxxxxxxxxx> ]
Sent: Friday, April 27, 2001 1:40 PM
To: Barry Male
Cc: stds-802-3-pwrviamdi@xxxxxxxx
Subject: RE: detecting a PD disconnection event

1a) was all of our favorites until Geoff's recent email regarding a patent

It may turn out that other methods are more cost effective when considered
My proposal is that more than one method could be used, not just the one
that we have been assuming.
My view is that we must at least consider alternative methods that do not
use DC current sensing.

- Rick

        -----Original Message-----
From:   Barry Male [SMTP:male@xxxxxxxxxxxxxxxxxxxxxx]
Sent:   Friday, April 27, 2001 10:29 AM
To:     Brooks, Rick [SC5:321:EXCH]
Cc:     stds-802-3-pwrviamdi@xxxxxxxx
Subject:        Re: detecting a PD disconnection event


        My preference is 1a.

        Have the PSE disconnect if the AVERAGE value of load current is less
10mA for a sample period of some time (say 100mSec)

        This averaging produces a robust detection method from the
standpoint of
system noise.



Barry Male
Senior Principal IC Designer          Internet: barry_male@xxxxxx
Power Management Products             NH Phone: 603.429.8705
Texas Instruments                     CT Phone: 860.844.8183
7 Continental Blvd.                   NH FAX  : 603.424.3460
Merrimack, NH  03054-0399 USA         CT FAX  : 860.844.8806

        On Fri, 27 Apr 2001, Rick Brooks wrote:

        > Just to start up another discussion, I wanted to find out how many
> would support
> the following concept for detecting when a PD receiving power becomes
> disconnected.
> the concept:
> $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
> 1) The PSE is responsible for detecting when a PD receiving DTE power
> becomes disconnected.
> If that event occurs, the PSE must turn off the power within some time
> (100ms to 500ms ballpark?)
> 2) The PSE may use any of the following methods to detect this PD
> event.
>       a) the DC load current drop below "X" ma (10ma?)
>       b) the ethernet link has dropped out
>       c) another proven method (pending discussion and feasibility proof)
>               some suggestions:
>               1) the AC probing circuit detects when the AC load changes
> (opens)
>               2) the PD modulation heartbeat current ceases
>               3) the PD response to a given PSE code is wrong or absent
>               4) other ideas
> $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
> Please voice your opinions on this concept.
> The motivation here is to lower the cost of delivering DTE power.
> thanks,
> - Rick

| Geoffrey O. Thompson                    |
| Chair IEEE 802.3                        |
| Nortel Networks, Inc.  M/S SC5-02       |
| 4401 Great America Parkway              |
| P. O. Box 58185                         |
| Santa Clara, CA 95052-8185  USA         |
| Phone: +1 408 495 1339                  |
| Fax:   +1 408 495 5615                  |
| E-Mail: thompson@xxxxxxxx               |
| Please see the IEEE 802.3 web page at   |