Also known as AC-3, Dolby Digital is an advanced perceptual coding technology for transmission and storage of up to five full-range channels (Left, Center, Right, Left Rear, Right Rear), plus a supplemental bass-only effects channel (referred to as a .1 channel due to the smaller number of bits needed for the information). It accomplishes this in less space than is required for one linear PCM coded channel on a compact disc. Dolby Digital is a more powerful and flexible coding system than AC-2 and provides a feature set including: 1) down mixing for optimal reproduction in mono, stereo, and Dolby Pro Logic compatible configurations as well as full 5.1 channel sound; 2) carriage of dynamic range and dialog level control information to decoders; and 3) operation over a wide range of bit rates. Dolby Digital can be heard on the soundtracks of a thousand plus films, and on the current generation of laser discs. Dolby Digital is being used on the audio tracks on DVD, and will be the standard audio on the new high definition television (HDTV) system going into operation in the United States.