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Re: [8023-POEP] Fw: Rejected posting to STDS-802-3-POEP@xxxxxxxxxxxxxxxxx

Hi all,


In addition to Martin questions and being more specific regarding the following:

  1. What is the system grounding policy? i.e. if all system segments PSE, PD, cables power supplies are on the same ground?
  2. If many PDs connected to a single Switch, are al PDs isolated from each other? i.e. No Dc current even the lowest (<100uA) is flowing through PDs via bad Isolation?
  3. What is the common mode noise between the positive and negative  leads to chassis?  (in PSE and PD)?
  4. If the cable contains a shield, doe's the shield is isolated from the PSE positive and negative leads?
  5. Is  the bob smith terminations is separate per channel or the capacitor part of the termination is common to many channels (ports) and is channel/port/pin is connected to that capacitor via resistor so from DC current point of view there is cross leakage current  between ports once a single port or more are on and mess the detection signal of other ports?




Darshan Yair
Chief R&D Engineer

Analog Mixed Signal Group

Microsemi Corporation

1 Hanagar St., P.O. Box 7220
Neve Ne'eman Industrial Zone
Hod Hasharon 45421, Israel

Cell: +972-54-4893019
Fax: +972-9-775-5111

E-mail: <mailto:ydarshan@xxxxxxxxxxxxx>.  



From: owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Patoka, Martin
Sent: Wednesday, July 08, 2009 3:44 PM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Fw: Rejected posting to STDS-802-3-POEP@xxxxxxxxxxxxxxxxx


Hi Bob,


It sounds like you have additional information about the incident not included in the liason letter.


What can you tell us about the electrical environment of the PSE, channel, and (non-PD) end-point device discussed in the liason?  What can you tell us about the physical channel implementation?


Can you provide the specific requirements that you allude to in your posting?


Thanks and Regards,



Martin Patoka
Systems Engineering Manager
Texas Instruments
O: 214-567-5487



From: owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Robert E Lounsbury
Sent: Wednesday, July 08, 2009 5:53 AM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: [8023-POEP] Fw: Rejected posting to STDS-802-3-POEP@xxxxxxxxxxxxxxxxx

----- Message from Robert E Lounsbury <relounsbury@xxxxxxxxxxxxxxx> on Wed, 8 Jul 2009 06:38:06 -0400 -----


Hugh Barrass <hbarrass@xxxxxxxxx>


owner-stds-802-3-poep@xxxxxxxx, STDS-802-3-POEP@xxxxxxxxxxxxxxxxx


Re: [8023-POEP] Liaison letter from IEC TC65/SC65C/JWG10 - Power over Ethernet performance in industrial environments

Hello  Hugh, Dave,

Please read the liaison letter.  Please disregard the damaged device.  The damaged device only served to start the discussion in IEC.  The letter is asking two very basic questions that might precipitate some considerations in the specification.  First Dave mentions noise coming from the device loads back onto the channel. This was one of the questions in the letter.  Dave alludes to violating the specification.  Please point to where in the specification where noise produced and coupled back to the PoE channel is defined, limited or otherwise discussed.  Second the letter asks if the PoE TG has considered analyzed what might happen if there is Radiated, conducted or other environmental noise in the area where the PoE system is installed might cause problems during the probing process. This has nothing to do with any design flaws of a product but merely the environment.  If you consider Industrial noise levels as defined by IEC out of the scope for 802.3at, then please respond indicating so. Then we might be in a position to disallow PoE in industrial.    Thanks for your time

Bob Lounsbury
– Principal Engineer
  Control and Visualization Business
  1 Allen-Bradley Drive, Mayfield Heights, OH. 44124

  Tel:    +1.440.646.4297

  Fax:   +1.440.646.3076

  Cell:   +1.440.610.4485


Hugh Barrass <hbarrass@xxxxxxxxx>
Sent by: owner-stds-802-3-poep@xxxxxxxx

07/07/2009 01:51 PM

Please respond to
Hugh Barrass <hbarrass@xxxxxxxxx>






Re: [8023-POEP] Liaison letter from IEC TC65/SC65C/JWG10 - Power over Ethernet performance in industrial environments





I can see that the liaison from IEC has caused some interesting
discussion amongst PoE experts (and myself), however I think that we are
being asked to comment on what may well be design flaws in specific
products and I do not think that is a healthy discussion within 802.3.

I suggest that we should send a reply along the following lines:


The problems described in your liaison spurred some vigorous discussion
amongst our task force members regarding possible causes for the damage
that you describe. However the members are not aware of any similar
reports that might indicate a systemic problem with 802.3 compliant
equipment. It is the opinion of the members of IEEE P802.3at Task Force
that the standard allows product manufacturers to build reliable and
interoperable equipment that will meet the requirements for supplying
power over Ethernet in many environments. However, the standard does not
define how a manufacturer must build the product to ensure reliability
or how an installer should ensure that the media is suitable for correct
operation within the standard. We suggest that you should work with the
equipment manufacturers involved to determine whether the failure is the
result of a systemic problem with the standard and whether a specific
amendment may be required.

With respect to the bit error rate performance of 802.3 links when power
is being supplied over the same link, the members of IEEE P802.3at Task
Force believe that a compliant system supplying power over an 802.3 link
will not perturb the channel sufficiently to degrade the performance of
the underlying link. However, it is the responsibility of the product
manufacturer to ensure that noise introduced by the load does not couple
to the link and violate the power over Ethernet specifications or the
channel specifications required for the link. Similarly it is the
responsibility of the system installer that the channel characteristics
are met in the presence of environmental noise.



David Law wrote:

>The IEEE 802.3 Working Group has received a liaison letter from IEC
>TC65/SC65C/JWG10, Industrial process measurement, control and
>automation/Industrial networks with respect to Power over Ethernet
>performance in industrial environments.
>I just wanted to inform you that I intend to delegate the generation of a
>draft response to the IEEE P802.3at DTE Power Enhancements Task Force
>during the plenary week in July. The draft response will be consider and
>then voted upon at the closing IEEE 802.3 Working Group plenary as part of
>the IEEE P802.3at closing report. You therefore may wish to review the
>letter prior to the meeting, the letter can be accessed at the URL [
>Best regards,
>  David Law
>  IEEE 802.3 Working Group Chair