What do you call a ghost that haunts a chemistry lab?
A methylated spirit.
A methylated spirit.
The magnetic stripe on your credit card
The black stripe behind a credit card contains important information about your bank account in magnetic code. Anything that de-magnetizes the stripe can wipe out the code and make the card unusable. Some common "de-magnetizers" are magnetic clasps on a purse or wallet, televisions, and stereo speakers.
A dirty or scratched magstripe
An erased magstripe (The most common causes for erased magstripes are exposure to magnets, like the refrigerator magnets or stereo speakers.
Start sentinel - one character
Format code="B" - one character (alpha only)
Primary account number - up to 19 characters
Separator - one character
Country code - three characters
Name - two to 26 characters
Separator - one character
Expiration date or separator - four characters or one character
Discretionary data - enough characters to fill out maximum record length (79 characters total)
End sentinel - one character
Longitudinal redundancy check (LRC) - one character
Start sentinel - one character
Primary account number - up to 19 characters
Separator - one character
Country code - three characters
Expiration date or separator - four characters or one character
Discretionary data - enough characters to fill out maximum record length (40 characters total)
LRC - one character
Merchants with few transactions each month do voice authentication using a touch-tone phone.
Electronic data capture (EDC) magstripe-card swipe terminals are becoming more common -- so is swiping your own card at the checkout.
Virtual terminals on the Internet
Merchant ID
Valid card number
Expiration date
Credit-card limit
Card usage
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The black stripe behind a credit card contains important information about your bank account in magnetic code. Anything that de-magnetizes the stripe can wipe out the code and make the card unusable. Some common "de-magnetizers" are magnetic clasps on a purse or wallet, televisions, and stereo speakers.
The magnetic stripe on the back of a credit card is often called a magstripe. It is made up of tiny iron-based magnetic particles in a plastic-like film. Each particle is really a very tiny bar magnet about 20 millionths of an inch long.
The magstripe can be "written" because the tiny bar magnets can be magnetized in either a North or South Pole direction.
Think of the magstripe as a piece of cassette tape fastened to the back of a card. Instead of motors moving the tape so it can be read, your hand "swipes" a credit card through a reader, or inserts it in an ATM machine.
A magstripe reader can understand the information on the three-track stripe. If the ATM isn't accepting your card, your problem is probably either:
There are three tracks on the magstripe. Each track is about one-tenth of an inch wide. Your credit card typically uses only tracks one and two. Track three is a read/write track (which includes an encrypted PIN, country code, currency units and amount authorized), but its usage is not standardized among banks.
The information on track one is contained in two formats: A, which is reserved for proprietary use of the card issuer, and B, which includes the following:
The format for track two, developed by the banking industry, is as follows:
There are three basic methods for determining whether your credit card will pay for what you're charging:
This is how it works: After you or the cashier swipes your credit card through a reader, the EDC software at the point-of-sale (POS) terminal dials a stored telephone number (using a modem) to call an acquirer. An acquirer is an organization that collects credit-authentication requests from merchants and provides the merchants with a payment guarantee.
When the acquirer company gets the credit-card authentication request, it checks the transaction for validity and the record on the magstripe for:
The cardholder enters a personal identification number (PIN) using a keypad to authenticate the transaction.
The PIN is not on the card -- it is encrypted (hidden in code) in a database. (For example, before you get cash from an ATM, the ATM encrypts the PIN and sends it to the database to see if there is a match.) The PIN can be either in the bank's computers in an encrypted form (as a cipher) or encrypted on the card itself.
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