DSL Filters ?

Bob Bruhns bbruhns at erols.com
Tue May 6 18:57:35 CDT 2003

Heh heh heh... well, we found out (the hard way) that an
"unfiltered" telephone on the DSL line would kill DSL communication.
The filters isolate the DSL signals from the speech circuitry in the

I GUESS the writers meant to say that the filters isolate the DSL
circuit from the erratic (read unknown) impedance of the speech
circuitry.  I imagine that a typical phone looks like a weird
multi-resonant shunt at DSL frequencies.  It just has to screw up
the eye pattern enough that the receive modems can't read the data,
and viola!  No DSL!

It's truly a shame how technical facts get garbled when communicated
by non-technical people.  And unfortunately, this is the norm.
Engineers try to express the situation accurately, and watch in
bemused dismay as the facts are misunderstood and twisted like the
eye pattern of the DSL signal when the filter is not inserted in
line with the phone.  Arrrgh!  After a few such experiences,
engineers tend to give up.  "...And the sense to accept what I can
not change," they sigh.

  Bob, WA3WDR

----- Original Message ----- 
From: "Andre Kesteloot" <andre.kesteloot at verizon.net>
To: "AMRAD Tacos" <tacos at amrad.org>
Sent: Tuesday, May 06, 2003 4:28 PM
Subject: DSL Filters ?

> Gang,
> DSL Line conditioners, or filters, are installed between the
> telephone line and each telephone set. The blurb states that "the
> in-line DSL filter eliminates all erratic impedance from telephone
> equipment that interfere with DSL".
> See for instance:
> http://www.suttleonline.com/pdfs/900SeriesAdapters.pdf
> Does anyone actually know what this is supposed to mean?
> 73
> André
> _______________________________________________
> Tacos mailing list
> Tacos at amrad.org
> http://www.amrad.org/mailman/listinfo/tacos

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