Which standard enables line-of-sight communication using infrared light?

• A. Bluetooth
• B. Infrared Data (IrDA)
• C. Radio Frequency Identification (RFID)
• D. Near Field Communication (NFC)

Answer: (D)

Infrared line-of-sight communication relies on light in the infrared spectrum and needs a direct optical path between devices. The standard that defines how this works is IrDA (Infrared Data Association), which established the protocols and physical layer for exchanging data over short-range infrared links. Because infrared signals travel in straight lines and can be blocked easily, IrDA is well-suited to devices that are in view of each other, like old laptops, printers, and infrared remotes. The other options use radio frequency energy rather than infrared, and NFC and RFID operate at very close ranges or rely on near-field magnetic coupling rather than line-of-sight IR.