Magnetism

Computers make extensive use of magnetism particularly in storage media. It is therefore not surprising that magnetism should be used as part of data capture. Here are some examples:

Magnetic Ink Character Recognition

Specially formatted characters are printed in a magnetic ink on the document. When the characters are passed through a magnetic field each produces a unique effect on the field and so is detected. MICR is accurate (few reading errors) is unaffected if the source document is dirty or creased and it is difficult to tamper with the data stored. It is however expensive to print the characters on the document. This method of data capture is used on schedules. This is the only significant use of the method because of its cost.

A cheque book is pre-printed with bank sort code, customer account number and cheque number. The value of the cheque is printed in MICR characters when the clearing bank processes the cheque, before it is read by the computer

Magnetic Stripe Cards

A plastic card with a magnetic strip on the back. The strip stores data that is read when the card is wiped through a reader. In the case of credit and cheque cards the magnetic strip will contain the account number, the type of card and the expiry date. Other uses of these cards includes security passes - where the card opens an electronic lock and the data read from the card can be used to keep track of where people have been - and sales promotions where customers collect points on their card every time they buy something.

In security and banking applications the user will have a changeable PIN number that is used to authorise the card's use. The PIN number is not stored on the card but it is held in encrypted form on the processing device.

Smart Cards

These are similar to magnetic stripe cards but the data is stored on a chip which is embedded in the card. These cards are sometimes called chip and pin cards.

Sensors

There are magnetic sensors used in things like door catches in burglar alarm systems.

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