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ENGINEERING

Fax and Context

Henry Petroski

The now-ubiquitous fax machine presents an interesting case study of the importance of context in technological developments. The idea of transmitting written, printed or graphical material over long distances is not new, as demonstrated by such ancient notions as winged messengers and carrier pigeons, and the more modern concept of the postal system. With the discovery of electrical phenomena and the development of such inventions as the telegraph and, later, the telephone, the transmission of words and word pictures by other than an animal or mechanical medium became a reality. Indeed, in the second half of the 19th century telegraphic messages could be carried over transoceanic cables. Telegraph offices served as terminals, which developed into centers to and from which young messengers such as Pittsburgh's Andrew Carnegie carried the printed documents. A message was encoded, transmitted, decoded and then transcribed to or printed on papers that were delivered to their ultimate destination by other messengers. The advantages of transmitting words in such a way were obvious to everyone, and especially to inventors. It was also obvious that one of the system's greatest shortcomings was that pictures and graphical materials could not be transmitted directly. Such a limitation of a technology sows the seeds of invention.

In 1843 a British patent for a method to transmit images electrically was granted to a Scots clockmaker named Alexander Bain. Bain was a prolific inventor who perfected the electric clock in 1840 and devised the inked typewriter ribbon in 1841. His inventive interest in both the electric telegraph and the synchronized electric clock prepared him to see how to combine their features into a pair of devices that could send and receive graphical material. As with the early versions of many inventions, Bain's facsimile machine was crude and clumsy by today's standards. The graphical material to be transmitted had to be prepared as a raised image on a metal block, much the way the reverse images of letters are raised from typewriter keys. A stylus was passed over the block and rose and fell in conformity with the raised image, thus breaking and making the transmission circuit. A synchronized stylus on the receiving machine was then raised and lowered to reproduce the image in another medium. By incrementally repositioning the transmission block in a second direction, the entire image could in time be reproduced. Bain's basic idea of scanning an image is preserved in modern fax machines, but the clear disadvantages of his first efforts drove subsequent inventors to seek ways to simplify his large and cumbersome machines and to reduce the effort needed to prepare images for transmission.

Among the first improvements was to replace the bulky, costly and difficult-to-prepare metal plates with tinfoil on which the image to be transmitted was drawn in ink. As the stylus passed systematically over the tinfoil, the current through the circuit was altered, and so the information could be transmitted electronically, to be recreated a line at a time on treated paper by a stylus incorporated into the receiving circuit. The first commercial facsimile system employing such a technique comprised a pair of machines installed in Paris and Lyons in 1865 by Abbé Caselli. No less an inventor than Thomas Edison was interested in improving the new technology, and he attacked the important problem of keeping the sending and receiving styluses in phase and synchronized by employing elaborate gearing and electromagnetic pendulums at each machine, which could be set in synchronized motion at the beginning of each transmission.

One of the limitations of using styluses was that they were principally on-off devices. This was fine for transmitting line drawings and graphs, but it was not effective in communicating the gradations of black and white that are contained in photographs, and so their images could not effectively be sent electronically. Near the end of the 19th century, however, the photoelectric cell was developed, and this enabled photographic images to be scanned and converted into a spectrum of electronic signals, thus transmitting shades of gray. As an added advantage, images could be sent faster, and Arthur Korn, a German inventor, first demonstrated the technique successfully in 1902. The transmission of photographs electronically had an obvious commercial appeal to newspapers, which were thus willing to invest in the new technology, and a wirephoto circuit was established by 1911 to connect offices in Berlin, London and Paris. Networks were established in Europe and the United States after World War I, and transatlantic transmission of photographs was established in the 1920s. In the early 1930s, The New York Times supported the work of the inventor Austin Cooley, who was developing a facsimile machine that was small enough to be carried by an individual to transmit news pictures via ordinary telephone lines.

One of the weak links in the chain of any newspaper-publishing enterprise is the printing and distribution network. The latter is especially capital- and labor-intensive because of the fleet of trucks and army of workers it requires to get the news delivered before it is stale. Newspapers have always been vulnerable to being shut down by strikes of printers and truckers, and a technological means of circumventing that had a clear appeal to publishers. The promise of being able to transmit facsimiles of newspapers around the clock to radio receivers in homes and offices led to the establishment by 1940 of 40 stations sending out experimental newspapers via ultra-high-frequency (UHF) transmission. These experiments were interrupted by World War II, and the emergence of television in the wake of the war led to the abandonment of commercial facsimile broadcasting by newspapers.

Facsimile transmission, albeit relatively crude and slow, was thus well established in specialized uses long before fax machines became the familiar instruments they are today. It is instructive to understand why a century of engineering and technological advances were not alone sufficient to give the system a more widespread presence. After all, typewriters and telephones were also crude by today's standards, and yet they pervaded places of business of all sizes and in all locations.








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