Types of Readers

There are many different types of readers in use today, we will briefly explain the various techniques employed by each.

The most common reader is called Proximity. These systems use cards or tokens as a means of identification. As the name implies, no direct contact is required between the card and the reader for the system to operate, the card must only be in the proximity of the reader. The read range will vary depending upon the card/token and the type of reader, from 1/2 inch to up to 3 feet, although the systems we typically install will work reliably within about 2 inches. The reader generates an RF field which causes specially designed wires in the card to resonate, transferring the card information to the reader. These cards are immune to electromagnetic and RF interference, and they can offer "hands free" operation.

Wiegand cards are essentially magnetic field effect devices. As the card is inserted or swiped through the reader an electromagnetic field generated by the reader induces a voltage in the card causing it to transmit its code. Unlike some insertion type systems, wiegand readers are completely sealed against weather conditions and as a result have a long life span. These cards are difficult to duplicate, highly damage resistant, and offer a high level of security.

Magnetic stripe cards use the same technology that is employed in credit cards, and are probably the most common type of card in use. There are two types of magnetic cards, low-coercivity and high-coercivity. The high-coercivity type are less prone to accidental erasure and damage. Magnetic stripe cards require that the card come in direct contact with the reader head causing wear and a shorter life span. This direct contact requirement also can cause misreads due to dirt and debris accumulation in the reader. Certain access control systems allow the user to utilize their existing credit cards, eliminating the need to purchase cards. The cards are low in cost but are easily duplicated, are affected by outside magnetic fields, and the readers require occasional cleaning to remove any dirt buildup on the read heads.

Bar codes, employ a pattern of bars and spaces of varying widths to represent the user information. This is the same technology that is used by stores for inventory control and check out counters. Since the bar code is visible it is easy to duplicate and as such is not considered to be a good choice for systems where security is a major concern.

Infrared cards contain a series of bar codes, similar to standard bar code cards, that are only visible when exposed to special infrared light. When the card is exposed to the special light, the bars cast a shadow behind the card which is then read by the reader. They are relatively low in cost, very reliable, not easily duplicated, and offer a good level of security but can be difficult to laminate for use as an ID card.

Keypads use a numeric pad, similar to that of a telephone. The user simply presses his code into the keypad and the system reads the numbers. This system does not require the user to carry any special card or token but can be less secure, since someone may see which numbers are being pressed. Certain keypads overcome this drawback by scrambling the number layout each time the keypad is used. Keypads can be used either by themselves or for high security in conjunction with some card reader technology. In this manner the user must both present a card and enter a code before access is granted.

Biometric systems measure some physical property of the user such as hand geometry, retina pattern, or voice pattern. These type of devices offer very high security but also are the most expensive and require that the user be present in order to be enrolled into the system.