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.
Jack Andresen
"Donald S. Stewart" wrote:
> Jack,
> 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.
>
> Regards,
> Don Stewart