That somethin' is very special indeed.
 
As far back in to 1980s someone discovered a technique 
whereby data could be recovered from magnetic media after 
erasure by ones and zeroes.  Basically it depends on the 
principle that magnetic media leaves a trace signature of 
its former state behind, even after it has been changed.
 
A engineer described the technique using an analogy by
saying:  "It works on the same principle that when a
rubber band has been stretched, even though it returns
to it's original size and shape, has properties that 
reveals it has been stretched before."
 
(Apparently, it works best on the original data that
was written to the disc the first time it was used.)
 
I'm not an engineer and neither have I performed such a 
recovery operation.  But I know it exists.

Tracy Johnson
MSI Schaevitz Sensors 

-----Original Message-----
From: Wayne R. Boyer [mailto:[log in to unmask]]
Sent: Wednesday, February 20, 2002 2:44 PM
To: [log in to unmask]
Subject: Re: [HP3000-L] rereading overwritten data...


Has anyone ever had experience with recovering data from an erased (via
binary 0s and/or 1s) drive?  Recovering from a crashed hard disc is
comparatively easy if you can control the heads and replace any damaged ones.
 If the normal heads in a drive would read only the binary 0s and 1s then
something very special would be needed to 'read' the overwritten data.

Wayne

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