What transmission method is often used in line-of-sight applications and is not susceptible to radio interference?

The transmission method commonly used in line-of-sight applications that is not susceptible to radio interference is infrared. Infrared communication relies on light waves in the infrared spectrum, which remain confined to the line of sight and are not impacted by traditional radio frequency interference. This makes it particularly effective in environments where clear line-of-sight is maintained, such as in remote controls, some forms of wireless data transfer, and specific applications in telecommunications.

Infrared technology, by operating in a different part of the electromagnetic spectrum compared to radio waves used by other wireless communication technologies, avoids many of the interference issues that can affect radio-based forms of communication. This characteristic leads to its reliability in controlled environments, where obstacles can be minimized and direct paths can be established.

In contrast, technologies like Bluetooth, Wi-Fi, and microwave transmission typically rely on radio frequencies, which can be easily disrupted by various forms of interference, including other electronic devices, physical barriers, and overlapping signals.