| Jeff McAdams on 4 Sep 2005 14:31:01 -0000 |
|
On Sun, 2005-09-04 at 03:05 -0400, Avijit Ghosh wrote:
> > This is a goofy question: What, if anything, would happen if two filters
> > were installed in series?
> Its a filter, I dont think anything will happen in the grand
> scheme of things. The first filter blanks out the bit that interferes w/
> the 8k bandwidth (or whatever it is) that is reserved for audio, and the
> 2nd filter also filters out the same thing to make it, well doubly clean
> so assuming the first filter works the 2nd makes it equivalent?
My only concern would be that, since these filters work well down in the
realm of analog waveforms, that the effect might not be that clear-cut.
The filters are low-pass filters, meaning that the lower frequencies get
passed, and higher frequencies get attentuated out.
Filters like this can never act in a completely binary manner...ie, it
either passes the frequency completely unattenuated, or completely shuts
down that frequency. Instead, they roll off the frequencies...at a
certain point the frequencies start to be attentuated a little bit, and
the frequencies get higher, they get attenuated more and more, until, at
some point, the frequencies are essentially being completely eliminated.
So, in that range between where the attenuation starts and where its
complete, a second filter will have an effect beyond what just a single
one would. Essentially, its going to make that roll off about doubly
steep. This might be good, actually, but I assume these filters are
designed to have the best possible effect for DSL and POTS on the same
line...so you may end up chopping out some of the high end of your
conversations with a second filter. I have no idea if it will be enough
to be noticeable, but its something to be aware of.
--
Jeff McAdams
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor safety."
-- Benjamin Franklin
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