Sound and pictures are converted into a digital format and compressed, using as few bits as possible to convey the information on a digital signal. This technique enables several television channels to be carried in the space used by the current analogue signals to carry one channel. Digital signals can be received by standard aerials, satellite dishes or via cable but have to be decoded and turned back into sound and pictures by using a separate set-top box, or a decoder built into your television (an integrated digital TV set/ iDTV).