Formerly known as CCITT, ITU (International Telecommunication Union) is the committee of the United Nations that was founded on May 17, 1865. Its job is to make sure all telecommunications devices (e.g., telephones, fax machines, and modems) can "talk to" each other, no matter what company makes them or in what country they're used.
For example, the Bell 212A standard for 1200-bps communications in North America is observed internationally as ITU-T V.22. For 2400-bps communications, the U.S. manufactures observe V.22 bis. name. In English, it is known as the international Telegraph and telephone Consultive Committee.
The ITU/CCITT has defined standards such as Group 3, Group 4, H.323, V.21, V.22, V.22bis, V.23, V.26, V.26bis, V.27, V.27bis, V.27ter, V.29, V.32, V.32bis, V.34, V.42, V.42bis, V.90, V.92, X.25, X.400 and X.500.