Re: Signal vs. Idle debate (was: Here's a new idea)
I grant a lot of what you say. I disagree that we are talking high quality magnetics. It
does have a modest cost. How right is Geoff? I cannot believe there is no margin
especially with respect to advanced chips.
If we do spare pairs then why not minimize effects by sending balanced power.
"Donald S. Stewart" wrote:
> You wrote,
> > I don't see it that way. Any scheme of idle pairs mid band insertion runs into
> > exactly the same problems as phantom power. Both schemes have to address the
> > compensation required to maintain Cat5 performance through the additional connectors
> > necessary to insert power.
> I see an idle pair scheme as having fewer problems than a signal pair
> (phantom) scheme. The important difference in the mid-span insertion
> configuration is that by using spare pairs one does not have to interject a
> new signal (power) into the signal leads. This injection most certainly
> will require ADDED high quality magnetics. This introduces added cost and
> potentially affects signal quality. Whether signal quality is affected is
> subject to evaluation. But as I recall Geoff Thompson stating at the last
> meeting, there is no degradation allocation or budget to consume. Therefore
> judging the acceptability of any degradation will be difficult. Power
> inserted on the spare pairs has additional coupling loss to the signal
> leads and its insertion should be less expensive. Both approaches run into
> the same issues regarding connectors.
> Don Stewart