Re: [8023-POEP] What's the max voltage drop thru a midspan?
Hi Steve,
Do you think the following text contained in the third from last paragraph
of subclause 33.4.8 'Midspan PSE device additional requirements' of IEEE
Std 802.3-2005 covers what you are looking for:
---oo000oo---
Configurations with the Midspan PSE in the cabling channel shall not alter
the transmission requirements of the "permanent link." A Midspan PSE
inserted into a channel shall provide continuity for the signal pairs. A
Midspan PSE shall not provide DC continuity between the two sides of the
segment for the pairs that inject power.
---oo000oo---
Regardless, I agree that the IEEE 802.3at specification will need to be
written carefully to ensure that, for example, it doesn't retrospectively
place a higher current carrying requirements on existing IEEE Std
802.3-2005 compliant Mid-Span PSEs.
Regards,
David
owner-stds-802-3-poep@xxxxxxxx wrote on 10/06/2006 05:34:39:
> Guys,
>
> As you all know, we're planning to run current from the endspan thru the
> midspan in a 4P system.
>
> Although I think its unlikely that we'll see Af-midspans with fused
traces
> or delaminated boards, technically we can't prove that it won't happen
> because 802.3af doesn't specify a min current rating for this path.
There
> seems to be no max limit for dc resistance either. (If these specs are
in
> 802.3af and I've missed them, then someone please point me to the
applicable
> table or paragraph.)
>
> We should make sure 802.3at specifies both these parameters. (But only
for
> midspans that output >15.4W so we're not retroactively putting new
> requirements on Af-midspans.)
>
> Any comments?
>
> Steve
>
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