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 revised version of H.320 introduces a number of enhancements and clarifications to the previous version, primarily the description on the usage of ITU-T Recs G.722.1, H.239, H.241, H.264, and ISO/IEC 14496-3 in H.320 systems.