The RF output on many home entertainment devices is used to connect those devices to a television or other component using a coaxial cable. These outputs combine both audio and video signal into a single stream of information within the cable.
Though it has fallen out of use by many manufacturers, some televisions and other devices still support RF, or coaxial connections. This is due to the likelihood of various consumers still possessing equipment that simply has no other means of connecting to a television. The motivating factor behind the change has to do with the vulnerability of coaxial cable to external interference as well as its limited video and audio quality. More advanced cable connections and video and audio outputs are available, ranging from simple component cables to more complex HDMI ports. As well, the advent of high-definition images and stereo audio programming has made the use of coaxial cables obsolete in many of their common applications. As a result, television manufacturers often choose not to include this component in their products simply because it is an unnecessary addition in many scenarios. Indeed, most of the televisions that would have once had a place to connect from an RF output no longer have this function.