 discussion with this final thought: Prior to the December 1990 approval of H.261, customers displayed unwavering brand loyalty to specific codec manufacturers. In 1991, the first H.261 compliant codecs made their debut. By June 1992, all major North American, European and Japanese codec manufacturers supported the standard. The H.261 codec is, today, the fulcrum of video communication technology. Even at 112 Kbps or 128 Kbps speeds, H.261-based systems reliably interoperate. They yield acceptable resolution, audio, and motion handling with a degree of quality that is more than adequate for most business purposes. THE REST OF THE FAMILY The formal title of the H.320 Recommendation is "Narrow-band Visual Telephone Systems and Terminal Equipment." The H.261 Recommendation is only part of the original H.320 family, which was ratified by the CCITT in December 1990. Also included in the original specification are H.221, H.230 and H.242-and two audio encoding specifications, G.711 and G.722. In November of 1992, the ITU-T added several new recommendations to the H.320 standard. One is H.231, which defines a multipoint control unit for linking three or more H.320-compliant codecs. A second is H.243, which describes control procedures between H.231 multipoint control units and H.320-compliant codecs. In March 1993, the ITU-T approved G.728, which defines how H.320-compliant codecs will handle 16 Kbps toll-quality audio. G.711, G.722 and G.728 are discussed in Chapter 6. H.221 "Frame Structure for a 64 to 1920 Kbps Channel in Audiovisual Teleservices" is the formal name for H.221. Its framing recommendation, perhaps the second best known of the ITU-T's H.320 family, defines the frame structure for a video bit stream across one or more 64 Kbps B channels. It acknowledges the ITU-T's HO (switched Standards for Videoconferencing 384 Kbps) dialing and other recommendations such as H11 (switched 1.536 Mbps) and H12 (switched 1.920 Mbps is available only in Europe). H.221 also defines a protocol that allows a single B channel t