"Narrowband Visual Telephone Systems and Terminal Equipment" is the summary ITU-T recommendation for standard videoconferencing using ISDN or similar telephone circuits. Based on Discrete Cosine Transform, CCM and motion compensation techniques. It can be a video system's sole compression method or supplementary algorithm, used instead of a proprietary algorithm when two dissimilar codecs have need to interoperate. H.320 includes a number of individual recommendations for coding, framing, signaling and establishing connections. It also includes three audio algorithms, G.721, G.722 and G.728.