credit cards

Why can’t I put my credit card on that scanner that says I can’t? In a clothes store for example.

if im thinking of the scanner that your talking about its because it is magnetized. credit cards may not work again if that strip on the back is close enough to a magnet

I’ve had my credit card demagnetised (or whatever the proper term is) by a hotel swipe-card room key before. That was a right pain.

To expound a little:
The black strip you see on the back of a credit card, ATM card, and other “swipe” cards holds various information about you and your account and is encoded magnetically. It’s called, stangely enough, a mag strip or mag stripe. Swipe readers (ATM’s, POS terminals, etc) read the information from the mag strip to validate the card and process the transaction. The reader is looking for data in a particular order and format. Any object which generates a strong enough magnetic field, like some scanners, can interfere with the magnetic field on the card literally rearranging or erasing some or all of the data. When you subsequently swipe the card the data read is garbled or missing causing the reader to reject the card.

Think of your card (at least the stripe) as a floppy disk and the reader as your PC. It works in a very similar manner.

Thanks Doc.

Yeah, we discussed here how certain wallets can delete info on them too.