[802.3af] specing polarity
I propose we tell designers to test their PSE and their PD both
to the 'Hot' - Opposite polarity and be done with this.
so here is the text:
The PSE must tolerate the application of a voltage of equal and
opposite polarity to its
own without incurring any damage when such potentials are applied
for an indefinite amount of time.
some vendors (chips and system) already have put together hardware
with opposite polarity to what we all agree to, and feel like we do not
the right thing going here.
also for such a scenario to take place the following has to
1- Both PSE's must fault (not discover before powering) or both be '
we worked hard to insure this does not happen --in
2- We have a parallel diode that we specd (paid for) at the PSE end that
of a hot-plug the current can return to the
At the same time the diode helps a PSE discriminate by
polluting anything in the other PSE
that resembles a signature insuring no false discovery of
another PSE.... No Hope here this
better be reality or we are in bad shape.
3- Even with all PSEs following a single polarity a cross over
cable would take us back
to the same problem again?!- if the PSEs are Hot -
what am i missing.
That was my 2c for today,