This Recommendation specifies technical requirements for narrow-band visual telephone systems and terminal equipment, typically for videoconferencing and videophone services. It describes a generic system configuration consisting of a number of elements which are specified by respective ITU-T Recommendations, definition of communication modes and terminal types, call control arrangements, terminal aspects and interworking requirements. This revision reflects the progress in relevant H‑Series Recommendations such as G.723.1, G.729, H.262, H.263, H.310, H.322, H.323 and H.324.