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 less secure since unless the user is very careful 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 use 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.