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RE: detecting a PD disconnection event

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]
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