entually, Study Group XV selected a hybrid-coding scheme that became the foundation for H.261, the "Video Codec for Audiovisual Services at Px64 Kbps." H.261, and five other recommendations, were submitted to the CCITT during its July 1990, meeting in Geneva. In December 1990, the CCITT approved all six recommendations, and formally declared them the H.320 family of standards. H.261 Study Group XV considered many issues as they developed the H.261 specification. First, they recognized that the market for video communication services would benefit from a global standard. Second, since ISDN B channels were internationally deployed, they found these digital circuits, used individually or aggregated, to be the ideal transport mechanism. Third, they knew that a compression specification would not achieve broad acceptance if it were not adaptable. By adaptable we mean two things: flexible enough to permit various elaborate and inexpensive implementations and versatile enough to incorporate new technologies as they become available. The H.261 standard meets these criteria. It accommodates globally disparate digital network and television standards. Many, if not most, H.261-based implementations use ISDN B channels, just as the CCITT predicted. The products built on H.261 are diverse. Some implement the Recommendation's optional procedures for delivering superior resolution and motion handling while others omit them to reduce cost. H.261 has proven to be flexible enough to accommodate ongoing advances in technology. As chips get faster, frame rates can increase and motion handling can improve without imposing fundamental change on the standard. H.261 can be a video system's sole compression method. It can also be ancillary and Video Communications: The Whole Picture thereby used as a substitute for a proprietary algorithm when two dissimilar codecs must interoperate. H.261 and CCIR Recommendation 601 The Consultative Committee for International Radio developed Recommendation 601 as an international specification for the 