ITU
Formerly known as CCITT, ITU is the Committee of the United Nations. Its job is to make sure all telecommunications devices (like telephones, fax machines, modems and so on) can "talk to" each other, no matter what company makes them or in what country they're used.
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.
- The official ITU page can be found at http://www.itu.int
Also see: Cell phone definitions, LAPM