While buying some groceries, I swiped my ATM card in the magnetic card reader, only to receive an error message. Tried it a few more times, with the same result. Next, I tried a trick that a clerk in another store had showed me. I wrapped the ATM card in one of the store’s thin plastic bags and swiped it again. Success! My question is, why does this trick work? Usually, any foreign material between a reproduce head and the magnetic media just makes things worse.
I want to know why this works, too. My ATM card has been acting up as of late (gotta get a new one…grrr.)
There have been several threads on this issue. Try search. I don’t recall that we ever got to a truly expert-who-knows conclusion, but there were some decent engineering theories.