A set-top box helps decode images and audio that comes from terrestrial digital signals, satellite signals, coaxial cables or the Internet so that they can be displayed on a television.
Old televisions with cathode ray tubes only had analogue decoders. As the transition from analogue to digital occurred, at different times in different EU countries, a set-top box had to be purchased as a retrofit to keep old analogue televisions in use. These are the set-top boxes that are subject to EU ecodesign rules.
Digital televisions that are now on the market generally include both a terrestrial and a satellite decoder, which means that a set-top box is no longer necessary.
When a television signal is delivered with ‘conditional access’ by specific providers, requiring a registration and a fee payment, a specific decoding product is necessary, called a ’complex’ set-top box.