H.231 is an International Telecommunication UnionITU-Tstandard for audiovisual systems. H.231 deals with the control of multipoint connections and is used in the H.320, H. 321 and H.322video conferencing standards. The title of the standard is: Multipoint Control Units for Audiovisual Systems using Digital Channels. The standard is designed for ISDN data rates for the multiplex channel with up to 1,920 kbit/s. It covers the control and monitoring functions of Multipoint Control Units ( MCU).