(I guess that also applies to some ATM's and other card readers.)
because they can scan quickly and if you leave the card in, it cancels it because it keeps reading the same thing over and over.
Your credit card has a magnetic stripe on the back of it that contains a string of numbers (such as 1425378404). Certain types of manual card readers, such as those on gas pumps, read the magnetic stripe on your card as you pull the card out rather than when you put it in. The card reader works best when you quickly pull the card out because the numbers all come in as one quick string and the reader can definitely tell the beginning and end of the number. (begin, 1425378404, end). If you pull the card out too slowly or erratically, the reader can get confused, and lose track of the beginning and end of the string. (begin, 1425,,,end?begin?378404 end?) Card readers that are motorized, such as those used in major ATMs, don't have this problem. The motor grabs and returns the card at the same speed every time, assuring a consistent reading of the card.
