Unlocking the mystery of Magnetic Stripe keycards

You hand out hundreds of keycards to your guests, but do you really understand how keycards work? There is frequent confusion and doubt surrounding the humble magnetic stripe. What is it? How do you spot a good one? What factors affect their performance?

In access control and banking, magnetic stripe cards have been around since the 1960’s. The hospitality industry started moving away from traditional metal keys to cards since the mid 1980’s. While other card technologies are forging ahead and gaining widespread acceptance, the magnetic stripe card due to shear numbers is by far the most widely used card worldwide.

Here are the basics. A magnetic card is a type of card capable of storing data by modifying the magnetism of tiny iron-based magnetic particles on a band of magnetic material on the card. The magnetic stripe, commonly referred to as a magstripe, is read by physical contact and swiping past a reading head. Magstripe cards are commonly used in credit cards, id cards, transportation tickets, keycards, gift cards, and much more.

MagStripe cards are governed by the International Standards Organization (ISO) under the following principles: ISO 7810, ISO 7811, and ISO 4909. These standards define physical properties of the card, including size, flexibility, location of the magstripe, and its characteristics. ISO also provides the standards for financial cards, including the allocation of card number ranges to different card issuing institutions.

On keycards, the magnetic stripe records the data at the front desk encoder and this data is later retrieved by the card reader inside the door lock. Sounds simple enough, so what can cause the card to produce a red light instead of a green light at the hotel room door? The answer is a bit more complicated as there are both card and reader aspects that can cause keycard failure.
The card itself can fail due to quality or mishandling. Some quality issues to look for in a card are opacity, magstripe surface & profile, and dimensions. The card must be opaque enough to avoid the transmission of light. The card encoders use light to detect the position of the card. A clear card would be indiscernible by the card reader impeding proper encoding or reading.
The surface of the magnetic stripe is also extremely important. Tests have revealed that magstripes that are flush on the card perform better than cards with rolled on or surface applied magstripes. You can test this by running your fingernail along the edge of the magstripe and the card. The surface should be smooth and no ridge or bump should be present. To encode and read successfully, the surface of the magstripe itself should be very smooth and not show any dust or particles. These foreign objects would have
become part of the card during the card lamination process and can interfere with proper operation of the card. Another way to check for a flush magnetic stripe is to try to scratch it off. On an ISO compliant card you will not be able to remove the magnetic stripe by scraping with your fingernail.

The dimensions of a card should also clearly follow the ISO standards. A card that is too small will not position itself in the correct place for reading or encoding. A card that is too large will not fit into the equipment. Thickness is also an important factor, cards that are too thick will damage the equipment and wear out the card prematurely. A thinner card may not make proper contact with the reader head.

Equipment factors that can affect the performance of the card are flux transition, jitter, and signal amplitude. These terms refer specifically to the encoded information on the card that is recorded in a barcode format. Special equipment can be used to read this barcode and determine if there is a problem in equipment performance.

Flux transition refers to the quality of the barcode encoded on the magnetic stripes which should be clean and crisp, not fuzzy or smeared. Jitter refers to the distortion of the information on the card while encoding. This can be caused by improper swiping though the equipment when encoding or by a rough surface on the card. Think of jitter as a bump in the road as it passes though the encoder. Signal amplitude is the ability of the magstripe to receive data and present it at the proper volume. These 3 tests may be able to determine if your equipment needs servicing or if it is simply operator error.

Lastly and maybe the most crucial and frequent factor in the performance of your keycard is the manner in which the card is handled and stored after it is encoded. It is possible to erase the encoded information with a magnet. Magnets today are present in many hidden places like wallet fasteners, cell phones with speakers, and money clips to name a few. The handling of the card will also affect the performance. A card that has been bent, cut, or damaged will not properly read in the lock.