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Dear Brian,<br>
All digital media have
some form of error-correction, it is built <br>
into the "standard." It is one stage
up from "error detection", in <br>
which you know a fault has occured, but you
cannot correct it. (The <br>
ISBN Book Numbering system, for example, has
error detection which <br>
will sound an alarm if one digit is changed or
two transposed, so you <br>
know you've typed something incorrectly; but you
don't know *what* has <br>
gone wrong). MS-DOS, Compact Disc, R-DAT, etc.
have error-*correction* <br>
built into them to match the kind of errors one
might reasonably <br>
encounter (large ones at nearly the same place
for CD, much shorter <br>
ones affecting consecutive tracks for R-DAT,
etc.) Error *correction* <br>
is built into the medium and automatically
invoked whenever you <br>
reproduce something.<br>
But to know *how*
something is degrading, one needs to get at the <br>
digits *before* error correction. Our CD Tester
does this. Audio CDs <br>
have two "layers" or error correction
(CD-ROMs have three), and our <br>
tester lists *all* the errors, where they are,
and whether they cross <br>
the threshold into audibility. By repeatedly
putting the CD into the <br>
tester every year (or whatever), and
printing-out the results, one can <br>
get a picture of how fast it is degrading, and
clone the data when it <br>
is approacing audibility.<br>
Because we haven't much
money, ours is a cheap CD Tester, a Model <br>
CDA2000 CD Analyser made by CD Associates, Inc.,
15A Marconi, Irvine, <br>
California 92618. email:
<<a href="http://www.cdassociates.com/" eudora="autourl">www.cdassociates.com</a>>.
We clone our R-DATs <br>
onto CD-R as soon as we get them home to
minimise the risks; I expect <br>
R-DAT (and PCM-701) tape testers exist, but we
don't use them.<br>
The difficulty is that
one doesn't get any understanding of *why* <br>
something is failing. A much more expensive
*analogue* tester is <br>
needed, which measures the *quantities* of
things like reflectivity, <br>
edge-sharpness, carrier-to-noise ratio, etc.
These are *analogue* <br>
measurements, and equipment which can do these
is at least five times <br>
the price; I'm afraid I have no experience of
it.<br>
Peter Copeland<br>
<br>
<br>
______________________________ Reply Separator
_________________________________<br>
Subject: Re: arsclist how to archive your language and other
matters<br>
Author: Brian Levy <xernaut@yahoo.com> at Internet <br>
Date: 16/10/2000 10:36 AM<br>
<br>
<br>
One more thing:<br>
such digital error correction and monitoring, how expensive and from
where <br>
would one get such equipment?<br>
<br>
bl<br>
<br>
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</blockquote>
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<font face="Century Gothic, Avant Garde">------------------------------------------<br>
Brian Levy<br>
Cultural Activist<br>
Kiwat Hasinay Foundation:<br>
Preserving Caddo Heritage<br>
211 W. Colorado Ave.<br>
Anadarko, OK 73005 USA<br>
(1) 405-247-5840<br>
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