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Credit card Magnetic strip and the plastic bag trick

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  1. Jun 18, 2013 #1
    When my credit card magnetic strip is worn it won't scan at the grocery check out. The clerk then uses a plastic bag over the card and runs it through the scanner. I'm baffled why this should work, but it does every time. Any explanations ?
    Thanks
     
  2. jcsd
  3. Jun 18, 2013 #2
    This is a fault of your card rather than their scanner?
     
  4. Jun 18, 2013 #3
  5. Jun 18, 2013 #4
    Yes, a problem when a card gets old. I'd think it happens to everyone.
     
  6. Jun 19, 2013 #5

    sophiecentaur

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    The separation by the bag must be, effectively, a low pass filter - reducing noise and 'sidebands', due to the scratches (modulation of the basic stripe frequencies). It can't be more than that. I don't know why the scanner couldn't do this for itself, in a more efficient and adaptive way. Maybe the newer generation scanners work better. It would need a 2D array of sensors to do best.
     
  7. Jun 20, 2013 #6
    I think you would still come to the same situation, but with a card more scratched up, after a time.
     
  8. Jun 20, 2013 #7

    sophiecentaur

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    Hopefully, the card would be out of date by that time. :wink:
     
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