Security passcards are commonly used to restrict access to specific areas or buildings and are encoded to fit the specific needs of the restrictor. In major cities, such as New York City, where buildings are often large and areas of restricted access within an office building are important to security, passcards are nearly a necessity for a safe and productive workspace.
come in a variety of types including general access cards, which do not contain individualized information about the cardholder, and individually encoded cards, which contain specifics about the cardholder and his or access clearance information.
Some data that may be encoded into an individually encoded card might include one’s name, an identification number such as a social security number or area-specific number, and an access level indication. Depending on the type of security systems in a space, an individually encoded access card may grant one access to one area but not another.
Individually encoded security passcards are relatively simple for the user, but involve a complex security system in their creation. Most individually encoded security passcards look like a credit card – they have a stripe on the back of the card called a magnetic stripe or “magstripe”. The magstripe is actually made up of iron-based magnetic particles in a plastic film. Each particle within that stripe is approximately two hundred millionths of an inch, and they are aligned on a plastic film similar to that in an old cassette tape.
When a security passcard is written, the particles within the magstripe are magnetized. Particles on the magstripe may be magnetized on either a north or south pole direction. If the polarity of the bars aligns, the card is blank and no information is remitted from it. Information is written in a process called flux reversal, wherein an encoder is utilized. The encoder contains an electromagnet, which acts as the encoding head. In the encoder, a N-N or S-S magnetization is written, and the strength of the magnet within the bars is changed thus creating data on the card.
The only machine able to read the information on a passcard is a card reader. The reader understands the changes in magnetic field created in the flux reversal process.
There are three types of passcard readers. In the swipe reader, the card is passed through a long narrow slot, which is open at each end. In an insert reader, the card is inserted into the machine to be read. In a proximity reader, the card only has to be tapped against the reader to be read.
Other types of cards include those where a radio transmitter has been embedded in the card. These cards are either battery powered or they rely on a radio receiver for power. When such cards are near the radio receiver, the security system signal is transmitted and access is granted. However, cards which utilize magstripes are the most common types of passcards in use today.