RE: Signal vs. Idle debate
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`RE: Signal vs. Idle debate
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`To: stds-802-3-pwrviamdi@xxxxxxxx
`Subject: RE: Signal vs. Idle debate
`From: "Larry Miller" <ldmiller@xxxxxxxxxxxxxxxxxx>
`Date: Mon, 08 May 2000 08:01:12 -0700
`Sender: owner-stds-802-3-pwrviamdi@xxxxxxxx
`
`(I sent this out last week but it didn't seem to make it into the
`reflector. Try #2:)
`Paul Yew and others,
`There are a number of Committee members that are concerned about (and,
`indeed, have serious reservations about) the probable side effects of
`superimposing comparatively high current DC on the signaling pairs. To date
`we have had no systematic demonstration by Cisco or anyone else that this
`arrangement is benign, and one of the charter items for the Committee is
`that the DC powering scheme chosen "shall not degrade the transmission
`environment".
`And, as it happens, Cisco apparently did not choose to adopt some of the
`isolation requirements that the Committee reaffirmed from existing 802.3
`standards.
`So it isn't quite such an opened-and-closed book situation as the marketing
`hype would have you believe. And the onus is on Cisco to provide enough
`information to make their case, the "trust us" statements appearing here
`notwithstanding.
`At the March meeting Cisco asked the question "what do we have to do to
`convince the Committee?". I have posted an answer to this at the IEEE
`802.3af public web site:
` http://grouper.ieee.org/groups/802/3/af/public/mar00/index.html
`It is titled "Recommended quantitative measurements of the parameters" and
`is comprised of extracts from IEEE 802.3 and ANSI TP-PMD specifications.
`These are the "numbers" that we all test our products against (hopefully)
`and constitute the criteria for which ANY scheme (not just Cisco's) will
`have to pass muster, in addition to the special requirements set forth by
`the Committee.
`I am sure that most of the Committee members are familiar with these
`criteria, particularly in view of the fact that many of the members
`participated in the standards committees that drew up these requirements in
`the first place.
`A solid presentation of measurements of these parameters in an actual
`operating system (with margins, not just PASS or FAIL results) would do a
`lot to give the Committee sufficient information to evaluate the viability
`of the Cisco design or any other that is proposed.
`(Comments on the requirements list are welcome)
`Regards,
`Larry Miller
`
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`http://www.ieee802.org/3/power_study/email/msg00122.html[6/12/2013 2:19:19 PM]
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