Re: detecting a PD disconnection event
O.K. I'll stick my 2 cents in for what it's worth.
Their patent states clearly that the current loop is created by existing
circuitry, (i.e. signal transformer) in the network device. Their artwork shows
clearly creating a current loop differentially on a pair, although the text is
ambiguous. 802.3af current implementation uses a current loop created with 2
pairs and common potential on both wires of each pair. It does not have to use
the current loop created by any common existing circuit, in fact, it requires
new circuitry to be added to work at all. In our implementation, hopefully,
there is no DC current flowing differentially through the signal transformer.
Has anyone checked to see if their system becomes non-functional if power over
MDI is implemented?
Sterling
"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.
>
> Jerry
>
>
> Gerard E. (Jerry) Bachand
> Avaya Inc.
> 300 Baker Avenue, Suite 100
> Concord, MA 01742
>
> (978) 318-6402 Voice
> (978) 318-6402 Fax
>
> <gbachand@xxxxxxxxx>
>
> 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
> wise.
> \Paul
>
> 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.
>
> Regards
>
> Jerry
>
> Gerard E. (Jerry) Bachand
> Avaya Inc.
> 300 Baker Avenue, Suite 100
> Concord, MA 01742
>
> (978) 318-6402 Voice
> (978) 318-6402 Fax
>
> <gbachand@xxxxxxxxx>
>
> 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
>
> Barry,
> 1a) was all of our favorites until Geoff's recent email regarding a patent
> issue.
>
> It may turn out that other methods are more cost effective when considered
> globally.
> 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.
>
> thanks,
> - 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
>
> Rick,
>
> My preference is 1a.
>
> Have the PSE disconnect if the AVERAGE value of load current is less
> than
> 10mA for a sample period of some time (say 100mSec)
>
> This averaging produces a robust detection method from the
> standpoint of
> system noise.
>
> Thanks
>
> Barry
>
> _________________________________________________________________
> 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
> people
> > would support
> > the following concept for detecting when a PD receiving power becomes
> > disconnected.
> >
> > the concept:
> > $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
> >
> > 1) The PSE is responsible for detecting when a PD receiving DTE power
> > becomes disconnected.
> > If that event occurs, the PSE must turn off the power within some time
> frame
> > (100ms to 500ms ballpark?)
> >
> > 2) The PSE may use any of the following methods to detect this PD
> disconnect
> > event.
> >
> > a) the DC load current drop below "X" ma (10ma?)
> >
> > b) the ethernet link has dropped out
> >
> > c) another proven method (pending discussion and feasibility proof)
> > some suggestions:
> > 1) the AC probing circuit detects when the AC load changes
> > (opens)
> > 2) the PD modulation heartbeat current ceases
> > 3) the PD response to a given PSE code is wrong or absent
> > 4) other ideas
> >
> > $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
> >
> >
> > Please voice your opinions on this concept.
> > The motivation here is to lower the cost of delivering DTE power.
> >
> > thanks,
> > - Rick
> >
> >