Magnetic strips now very common on all kinds of plastic cards. for example:

• Bank card
• Credit card
• Loyalty card
• Club cards
• Security passes

The reason they are so popular is that it is a very inexpensive technology - information is simply encoded in magnetic form on the strip. The reader picks up the information by swiping the card through it. The reader then inputs the information into whatever computer system it is connected to.

Example:

• EPOS in supermarkets
• Turnstiles on the Underground
• Doorways in secure areas
• Club cards in shops

Advantage:

• Inexpensive
• Robust - not easily damaged
• Simple to use
• Fast

Disadvantage:

• A card can be copied fairly easily.
• Sensitive to strong magnetic fields