Infrared remote controls were first developed in the late 1970s and use infrared light and photo receptors to send signals from the remote to electronic devices. They allow control of TVs, radios, DVD players, and other devices by sending different infrared light frequencies for different functions. Now infrared remotes can control many devices at once and have become common due to problems with earlier remote control technologies that required direct line of sight or could be affected by outside interference. Infrared remotes are used for entertainment, industrial applications, and military purposes like missile guidance.