The facsimile, or fax, machine is both a transmitting and receiving device that "reads" text, maps, photographs, fingerprints, and graphics and communicates via telephone line. Since 1980s, fax machines have undergone rapid development and refinement and are now indispensable communication aids for news services, businesses, government agencies, and individuals.
The fax was invented by Alexander Bain of Scotland in 1842. His crude device, along with scanning systems invented by Frederick Bakewell in 1848, evolved into several modern versions. In 1869 a Frenchman, Ludovicd'Arlincourt, synchronized transmitters and receivers with tuning forks and thus aided further developments. In 1924, faxes were first used to transmit wire photos from Cleveland to New York, a boom to the newspaper industry. Two years later, RCA inaugurated a trans-Atlantic radio photo service for businesses.
The use of faxes, and fax technology itself, remained comparatively limited until the mid-1980s. By that time, models either required an electrolytic or photosensitive paper, which changed color when current passed through it; or thermal paper, a material coated with colorless dye, which became visible upon contact with a toner. Updated models from the 1990s employ plain paper (which, unlike thermal paper, avoids curling) and are preferred for their superior reproduction. Another improvement is the invention of a scrambler, an encoder that allows the sender to secure secrecy for documents, particularly those deriving from highly sensitive government projects or secret industrial or business dealings.
Some fax machines are incorporated into telephone units; others stand alone; and still others are part of personal computers. These last models contain a fax board, an electronic circuit that allows the computer to receive messages. In the most common models, the user inserts the material to be transmitted into a slot, then makes a telephone connection with another facsimile machine. When the number is dialed, the two machines make electronic connection. A rotating drum advances the original before an optical scanner. The scanner reads the original document either in horizontal rows or vertical columns and converts the printed image into a pattern of several
million tiny electronic signals, or pixels, per page. The facsimile machine can adjust the number of pixels so that the sender can control the sharpness and quality of the transmission. Within seconds, the encoded pattern is converted into electric current by a photoelectric cell, then travel via telegraph or telephone wires to the receiving fax, which is synchronized to accept the signal and produce an exact replica of the original by reverse process.