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Thread: Extracting data from old data tapes

  1. #1

    Default Extracting data from old data tapes

    Last year I was helping clean out my grandmother's garage and I came across a briefcase that my late grandfather used for one of his jobs. Inside was a bunch of manuals for industrial equipment from the mid 80s-early 90s and a couple of data tapes. I managed to transfer them and they are live at https://archive.org/details/TheDataTapeFiles. The problem is that I have no clue how to extract the data from the tapes.
    I asked around and so far I gathered this information: the data itself is recorded at 300 baud and bursts at 12 second intervals, there is a carrier tone at about 2400hz that lasts for about four seconds and is quite unstable, and there is no filters done on the data itself. What makes this even harder is that a section of one of the tapes has been taped over with a recording of a loud machine. Luckily, the data track can still be heard so it may be recoverable. If anyone wants to mess with these recordings and see what you can make of them they are in that archive.org upload. Also audio warning for anyone who wants to listen to them. The first seven minutes of each tape are very loud and I think the way the tape drive was configured is to blame for that.

  2. #2
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    What sort of equipment did your grandfather deal in? I recall some early CNC gear used cassettes in place of paper tape, for example.

  3. #3
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    If you don't know the format/encoding, I would guess that the first step would be to perform a Fourier transform and see if you get something useful. I did a quick google search for "audio sample fourier visualization" and this was one of the top hits:
    http://www.geosci.usyd.edu.au/users/jboyden/vad/

    You could try searching on similar keywords to find more information.

    There's a strong likelihood that these tapes won't contain anything particularly interesting. They might just have copies of device configuration files containing a bunch of numbers that would be meaningless for anything except the specific machine they were intended for.

  4. #4
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    Sounds like plain old Bell 103 FSK. 2225 Hz for mark and 2025 for space. Very easy to decode--even easier if you've got an old 103-compatible modem with an audio coupler. Bell 103 encoding is still used today.

    I stored file for my Altair 8800 initially way back when using the guts of a Novation modem modified to use the same tones for originate and receive.

    The dead space in between blocks on your samples was probably done to allow data to be stored.

  5. #5

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    I looked up what was written on the tapes and apparently the WLP-200 is some kind of stretch wrapper, so it's likely that my grandfather was dealing with packing materials. As for the data sounding like it came from a Bell 103, is there a program I can use to test that out?

  6. #6

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    Hi, it's been a while. I think I finally found a lead to where these tapes came from. In the briefcase was also an Omron PRO15 PLC and the manual that went with it. There was even a section about playing and recording data tapes which all of the characteristics matched with the tapes I have. So there's a 90% chance that the data on them are just programs made for the PLC in question. I'm also rerecording the tapes using the settings mentioned in the manual and also with the jack that came with the controller.

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