What technology allows a contactless smart card to communicate with a reader?

Contactless smart cards utilize radio frequency technology to communicate with a reader. This method relies on the principles of electromagnetic fields to enable communication without the need for physical contact between the card and the reader. When the smart card is brought near the reader, it generates a field that powers the card and allows the data transfer to take place seamlessly.

Radio frequency communication is favored for contactless transactions because it facilitates quick and efficient interactions, making it ideal for applications such as payment processing and access control. The functionality of this technology involves a high-frequency signal that permits data exchange over a distance, usually within a few centimeters, enhancing user convenience and speed during transactions.

In contrast, other technologies like infrared communication do require line-of-sight and can be hindered by obstacles. Bluetooth technology is generally used for longer-range communications but is more complex and power-hungry for applications like simple payments. Visible light communication, though innovative, is not suitable for the intended purpose of smart card transactions due to its limitations in range and environmental dependencies.