Card reader:-

A memory card reader is a device used for communication with a smart card or a flash memory card. A business card reader is a scanning device used to scan and electronically save business cards. A magnetic card reader is a device used to scan cards containing magnetic data strips. A punched card reader is a device used to read holes in punched cardboard cards.
A smart card reader is an electronic device that reads smart cards. Some keyboards have a built-in card reader. There are external devices and internal drive bay card reader devices for PC. Some laptops have built-in smart card reader. Some have a flash upgradeable firmware. The card reader supplies the integrated circuit on the smart card with electricity. Communication is done via protocols and you can read and write to a fixed address on the card.
A barcode is a series of alternating dark and light stripes that are read by an optical scanner. The organization and width of the lines is determined by the bar code protocol selected. There are many different protocols but Code 39 is the most popular in the security industry. Sometimes the digits represented by the dark and light bars are also printed to allow people to read the number without an optical reader. The advantage of using bar code technology is that it is cheap and easy to generate the credential and it can easily be applied to cards or other items. The disadvantage of this technology is that it is cheap and easy to generate a credential making the technology susceptible to fraud and the optical reader can have reliability problems with dirty or smudged credentials. One attempt to reduce fraud is to print the bar code using carbon-based ink and then cover the bar code with a dark red overlay. The bar code can then be read with an optical reader tuned to the infrared spectrum, but can not easily be copied by a copy machine. This does not address the ease with which bar code numbers can be generated from a computer using almost any printer.
There are several forms of biometric identification employed in access control: fingerprint, hand geometry, iris and face recognition. The use of biometric technology significantly increases security level of systems because it eliminates such problems as lost, stolen or loaned ID cards, and forgotten or guessed PINs. The operation of all biometric readers is alike: they compare the template stored in memory to the scan obtained during the process of identification. If the probability that the template in the memory and the live scan belong to the same person is high enough, the ID number of that person is sent to a control panel. The control panel then checks permissions of the user and makes the decision whether to grant access or not. The communication between the reader and the control panel is usually done in the industry standard Wigand protocol. The only exception is intelligent biometric readers that do not require any panels and directly control all door hardware