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, such as the prevalent Code 39.[3] Sometimes the digits represented by the dark and light bars are also printed to allow people to read the number without an optical reader.
There are two types of smart cards: contact and contactless. Both have an embedded microprocessor and memory. The smart card differs from the proximity card in that the microchip in the proximity card has only one function: to provide the reader with the card's identification number. The processor on the smart card has an embedded operating system and can handle multiple applications such as a cash card, a pre-paid membership card, or an access control card.

A reader radiates a 1" to 20" electrical field around itself. Cards use a simple LC circuit. When a card is presented to the reader, the reader's electrical field excites a coil in the card. The coil charges a capacitor and in turn powers an integrated circuit. The integrated circuit outputs the card number to the coil, which transmits it to the reader.

Sometimes memories can fade in time, but then we can experience something which brings decade’s old memories flooding back. It could be finding an old photograph, the feel of something in our fingers, the sound of seagulls squawking overhead or the smell from a bakery wafting in the breeze as we are walking along the street. Then, just for a moment, it is as though we are right back in that once-forgotten moment, experiencing the joy and happiness as though reliving it.
The difference between the two types of smart cards is the manner with which the microprocessor on the card communicates with the outside world. A contact smart card has eight contact points, which must physically touch the contacts on the reader to convey information between them. Since contact cards must be inserted into readers carefully in the proper orientation, the speed and convenience of such a transaction is not acceptable for most access control applications. The use of contact smart cards as physical access control is limited mostly to parking applications when payment data is stored in card memory, and when the speed of transactions is not as important.

In the 1-to-1 mode a user must first either present an ID card or enter a PIN. The reader then looks up the template of the corresponding user in the database and compares it with the live scan. The 1-to-1 method is considered more secure and is generally faster as the reader needs to perform only one comparison. Most 1-to-1 biometric readers are "dual-technology" readers: they either have a built-in proximity, smart card or keypad reader, or they have an input for connecting an external card reader.
All biometric readers work similarly, by comparing the template stored in memory to the scan obtained during the process of identification. If there is a high enough degree of probability that the template in the memory is compatible with the live scan (the scan belongs to the authorized person), the ID number of that person is sent to a control panel. The control panel then checks the permission level of the user and determines whether access should be allowed. The communication between the reader and the control panel is usually transmitted using the industry standard Wiegand interface. The only exception is the intelligent biometric reader, which does not require any panels and directly controls all door hardware.
Many Windows users come across the SD card reader not working error after the Windows 10 update and fail to get access to their important SD card data. It's a very nerve-wracking but also common issue that Windows 10 is stuck on the “SD card not recognized” problem. Don’t be worried. In this Windows 10 guide, we’ll walk you through top 4 ways to tackle this card reader not working issue.