The FAX format is also referred to as CCITT Group 3 or Group 4 compression and many people opt for it either when they plan to prepare an image file for being sent by fax, or when they simply want to save space by converting to a bitonal format. CCITT is an abbreviation coming from the International Telegraph and Telephone Consultive Committee — the organization responsible for establishing several transmission protocols, including Group 3 and Group 4 which apply to black-and-white images. Among the image extensions which support the CCITT Group 3 and Group protocols, TIFF is one of the most popular.