Credit card Magnetic strip and the plastic bag trick

18
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
 
1,253
105
This is a fault of your card rather than their scanner?
 
18
1
Yes, a problem when a card gets old. I'd think it happens to everyone.
 

sophiecentaur

Science Advisor
Gold Member
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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.
 

256bits

Gold Member
2,863
923
.... I don't know why the scanner couldn't do this for itself, in a more efficient and adaptive way. ......
I think you would still come to the same situation, but with a card more scratched up, after a time.
 

sophiecentaur

Science Advisor
Gold Member
23,752
4,036
Hopefully, the card would be out of date by that time. :wink:
 

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