Re: no compromise?
Joerg-
As you say, "Theoreticly it should be possible to do
mid span phantom powering as well. This might require more effort in the
magnetics and eventually (but probably not) some signal conditioning."
But there is a long way between theory and practice.
There is currently very little margin in a Class D link for new elements.
Every new element that is introduced into a link has losses and mismatches.
In the cabling community the competition for the exisiting margins is
already oversubscribed by legitimate factions with very real needs.
Only some of these are:
Modular furniture manufacturers who wish to use 25-pair (or
higher) cable
Modular furniture manufacturers who wish another connector in the link
Hand held tester manufacturers who want testing margin
Category 6 cabling manufacturers who want improved performance in
new product and have backward compatibility with Category 5 and
interoperability between manufacturers.
Anybody who wants to put another connector in the link including
802.3af.
We have not seen any sort of rigorous worst case analysis on this yet on
the basis of just doing what WE want to do much less integrating it with
these other legitimate needs yet staying compatible with the installed base
of 100BASE-Tx.
Geoff
At 03:54 PM 5/5/00 +0200, WM wrote:
>Hello,
>
>Iīm not an expert in hardware design myself, Iīm just watching the discussion.
>As I understand thereīre two groups:
>group A prefers using spare pairs, to prevent existing investments into
>expensive switches etc.
>group B prefers phantom powering offering a pathb to 1000Base-T and giving
>a chance for installations using only 2 pairs, saying group A requires
>replacement of equipment.
>
>I donīt understand the conflict. Theoreticly it should be possible to do
>mid span phantom powering as well. This might require more effort in the
>magnetics and eventually (but probably not) some signal conditioning. Or am
>I wrong?
>
>In production volume that should be still a cheap solution and AVOIDS the
>need to replace existing switches/hubs etc., saves old installations in all
>buildings and still gives a migration path to 1000 Base-T.
>
>For new/replacement applications it could be integrated into the switch and
>would not influence the BOM at all (except for a bigger power supply)
>
>Best regards
>Joerg