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oxidestrip.jpg

Very cool trick from anaglyph: Apply powdered iron oxide to the magnetic stripe on a swipe card to visualize the encoded data. [via Boing Boing]

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Sean Michael Ragan

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I write for MAKE, serve as Technical Editor for MAKE magazine, and develop original DIY content for Make: Projects.


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  1. auBois says:

    I realize the cost in both dollars and people-time, but NASA has tapes for which there is no viable method for reading. It is also true that even if they COULD obtain the binary data from the tapes, the encoding method originally used may simply have been forgotten, the documentation for it destroyed which would make life VERY difficult. (and we won’t even comment on the tapes they “re-used” of the first landing on the moon for other purposes… Grrr!)

    One of the problems of reading these tapes (other than the fact that they are rather fragile) is that the data itself has become faint The Earth’s magnetic field obviously has an accumulative effect on the domains of the magnetic particles on the tape. As a result, it is a real bear to even CONSIDER creating a physical (electronic) tape reader that was sensitive enough to pick up the data.

    However, “iron oxide” (‘good old rust’) is ubiquitous. I have no doubt that for ‘reading’ these tapes that it would have to be extremely pure and be made into an exceedingly fine powder.

    OK – since this is all utterly a pie-in-the-sky concept (so, please don’t flame me for appearing to suggest something idiotic: I already know that it is), a section of tape would have its surface (lovingly) engulfed by a gentle fixative. The fixative would both keep the particles as much in the positions as possible as it would also protect the next stage of the machine. The more dust-free the photographic stage is, the better.

    This next stage would be nothing more, actually, than a photographic scanner. Ka-chunk, ka-chunk, ka-chunk, and so forth. You migh wish to re-spool the stuff that comes out, but it really probably isn’t worth it.

    OK, fine, dandy. I haven’t even mentioned stuff like print through: “The proximity of layers of tape on the spools of a cassette or reel to reel tape causes a weak imprint of magnetic information to be transferred to adjacent layers” from dictionary.babylon.com which means that the data might already be trashed.

    There is also this difficulty of data formatting – I was creating tapes for use to be used to fabricate a TI gate array from LMSC – my company (“You, Too, Can Have A Trident II Missile”). It was on some machine-or-other and they had to be able to read those on who-knows WHAT other machine – it took a moderate amount of fiddling around to get it to work. At least I had documentation to go by!
    —–

    I think this is a great article and it has been a pleasure to read. And that is a great photograph!

  2. craig says:

    I think the worst degradation to the magnetic data is the store clerk who slides your card back to you stripe side down. I swear when I get a brand new card, the first clerk I purchase from slides it on a metal surface back to me!
    Odd that a weak & worn card that will not read, works if it’s swiped with a plastic bag around it. Works every time.

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