An Encyclopedia of the History of Technology part 77 pps

PART FOUR: COMMUNICATION AND CALCULATION 742 exhibited the device in 1893–4, but thought of it as a mere novelty and failed to patent it in England. However, his choice of film width (35mm) and perforation design have become standard for normal-width motion pictures down to the present time. Robert Paul, finding the kinetoscope unpatented in Britain, copied the device and sold several to Charles Pathé in France. Edison, realizing his mistake, refused to allow Paul to use his films, stimulating Paul to build his own camera. Paul also constructed a projector with a Maltese-cross intermittent-motion system (the French astronomer, P.J.C.Janssen had used a revolver camera with a Maltese cross to photograph the transit of Venus in 1874). However, credit for the first successful motion-picture projection system is usually given to the brothers August and Louis Lumière of Lyons, who in 1895 designed a combined camera and projector to which they gave the name cinematographe. They used the same size film as Edison, but with only one round perforation at the margin of each picture, instead of the four square ones used by Edison. They also were the first to give an exhibition for which the public had to pay admission, in 1895. In 1896, Lumière films were projected in London by the magician Trewey, who was soon giving regular cinema shows; the films were only about 15m long (49ft), so frequent reel changes were necessary. In 1897, Pathé separated the cinématographe into two distinct parts: camera and projector. The Lumières were quick to capitalize on this new entertainment medium, buying up film manufacturers in France and creating production units in the United States and in Russia. Edison, reluctantly abandoning his kinetoscope, was persuaded by his distributors to buy the rights to a projector so his films could be shown before an audience, and not just remain a curiosity—the ‘peep-show’. Edison then threw his great organizational talents into the battle, and his company made 1700 movies. He also built the first studio, a rambling affair which could be rotated to follow the sun; it was called the Black Maria, because it was covered with tar paper to increase contrast. Even though Edison was also the inventor of the phonograph, and had been able to synchronize film and disc in his laboratories in 1889, the system was too awkward for commercial application. A sound-on-film system was patented by Eugène Augustin Lauste in France in 1906 and demonstrated in 1910, and a more advanced system shown by Lee de Forest of the US in 1923, but they did not have any commercial success. What many critics consider the golden era of the motion picture, the silent era, had a chance to flourish for quarter of a century. Another desired innovation was colour, and attempts were made from as early as 1898. Some films were hand-coloured using stencils, and the French tried tinting certain scenes for dramatic effect. However, although a number of two- colour processes were devised in the early part of the twentieth century, the first commercially viable full-colour film was not made until 1932 (see p. 736). INFORMATION 743 FACSIMILE AND TELEVISION While the practice of transmitting pictures over the air is relatively recent, the basic principles behind facsimile and television can be observed in nature, and have been used by man in his art for thousands of years. Many insects have compound eyes; that is, instead of just one lens to focus a scene on the optic nerve, their eyes are composed of thousands. This is the mosaic principle: a multiple of similar, tiny elements composes a single, meaningful whole. The great advantage of using fragments of minerals, glass or shells in art is that they are small, light and multi-coloured, yet can be used to cover immense, multiply curved surfaces with intricate designs, more brilliant than any painted surface, yet far more durable. Hence, mosaics were a natural choice in decorating early Christian churches. A mosaic design is another example of optical illusion; the eye is tricked into seeing the whole when it cannot distinguish individual elements. In today’s communications terminology, digital elements are used to represent an apparently continuous pattern. The same principle was applied to painting in the nineteenth century, particularly by Georges Seurat who used tens of thousands of different-coloured paint dots to depict outdoor scenes. The breaking up of a whole into tiny segments is also the basis of half-tone printing processes (see p. 679), and the underlying mechanism of video cameras. Another method of dissecting a whole into simpler elements is scanning, which transforms a spatial pattern into a temporal one. This is the technique we use in reading the printed page, and underlies facsimile and television transmission. The eyes move across a line of type, and ‘fly back’ to the beginning of the next line; similarly, the electron beam in a television receiving tube sweeps across it 625 times every 1/50 second to compose images, a sequence of which, due to persistence of vision, we interpret as a moving image, the close simulation of reality. However, the invention of television had to wait until the principles underlying motion pictures were better understood. Facsimile In contrast, facsimile ideas were being considered soon after the invention of photography and even before electric telegraphy; the basic inventions for the transmission of documents and still pictures were made 30 years before the telephone. In 1817 the element selenium was discovered by Berzelius in Sweden. In 1843, Alexander Bain, the Scottish watchmaker who invented the electric clock (see p. 696), patented an electrochemical recording telegraph, and in 1847, Frederick Bakewell devised the cylindrical mechanism on which images for transmission are placed for scanning, which also provided synchronization. Cylindrical scanning became the basis of most facsimile PART FOUR: COMMUNICATION AND CALCULATION 744 machines up to the 1980s. During 1861–2, Giovanni Casseli in Italy devised the pantelegraph, which was used by the French PTT to transmit images between Paris and Marseilles during the latter part of the decade. Willoughby Smith of the Telegraph Construction Company in England discovered in 1866 that light would lower the electrical resistance of a selenium rod. This, the photoelectric effect, is the basis of all facsimile and television systems. In 1877, Constantin Senlecq in France published a paper on his telectroscope, the first device to use selenium for scanning. Facsimile seems to have had a slow but steady evolution from that time, but during the early part of the twentieth century the major use was in transmitting photographs for newspaper publication, a process called wirephoto. It was not until after the Second World War that facsimile devices became available in offices. These desktop transceivers, called telefax, required six minutes to transmit a page over the public switched telephone system; in contrast, large centrally located systems known as bureaufax work at higher speeds between post offices, and use separate transmission and reception devices. In the 1970s the Japanese turned their attention to facsimile, after long frustration with attempting to use telex with the large character sets of their language. They now have a virtual monopoly on the manufacture of facsimile machines, which are capable of unattended transmission and reception at speeds of less than a minute per document. Television It was not long after the invention of the telephone in 1876 that imaginative writers and artists were dreaming of the next step, which they called by such names as ‘telephonoscope’ or ‘electric vision’. The French artist Albert Robia was especially entranced, and drew scenes of families watching a war ‘live’ in their living-rooms, people taking courses without going to school, and housewives window-shopping from an armchair. In 1884, eight years after the invention of the telephone, a German, Paul Nipkow, patented his ingenious disc, which had 24 holes evenly spaced along a spiral. While the disc spun at 600rpm a lens focused the light samples on a selenium photocell. The output of this cell was a varying electric current; to reassemble the now dissected image, Nipkow proposed using an identical, synchronously rotating disc and a Faraday-effect (magneto-optical) light modulator. Nipkow did not actually build this system (no suitable technology was available at that time), but the Nipkow disc was to become the basis of early mechanical television systems. In 1897 in Strasbourg, Ferdinand Braun constructed the first cathode-ray oscilloscope, the basis of all present television receivers. In 1907, Boris Rosing at the Technological Institute in St Petersburg proposed using Braun’s tube to INFORMATION 745 receive images, and A.A.Campbell-Swinton in a letter to Nature in 1908, ‘Distant Electric Vision’, proposed using cathode-ray tubes (CRT), as they became known, for both transmission and reception. Vladimir K.Zworykin, who had emigrated to the USA from Russia, joined the Westinghouse company in 1919, bringing with him ideas about using CRT devices for television. However, it was not until 1923, after having left and returned to Westinghouse, that he constructed the first practical storage camera tube, the iconoscope. The image was projected on to a mosaic of photosensitive elements inside the tube. This mosaic was then scanned by a beam of electrons which, by a process called secondary emission, released charged elements to form the picture signal. During the period 1923–4, Charles Francis Jenkins, who had contributed to the evolution of motion-picture projectors in the 1890s, experimented with the Nipkow disc. About the same time, but independently, John Logic Baird in Scotland was engaged in similar experiments. Baird, and Jenkins shortly after, made demonstrations of their systems in 1925, as did Ernst F.W.Alexanderson at the General Electric (GE) Company’s headquarters in Schenectady. In 1927, Philo T.Farnsworth, an independent inventor, demonstrated the first complete electronic television system, based on his invention of the image-dissector tube. However, Zworykin, now with the Radio Corporation of America (RCA), contested Farnsworth’s patent, and only after long litigation did each receive basic patents on their systems. These experiments came to preliminary fruition in 1927, when the presidential candidate, Herbert Hoover, appeared in an experimental AT&T telecast. GE put the first home TV set on the market in 1928, and the same year broadcast the first dramatic production, the sound going out over WGY while the picture was transmitted from experimental station W2XAD. This was followed by a science-fiction drama, giving its audience a missile-eye’s view of an attack on New York City. In 1929 the British Broadcasting Corporation (BBC) began an experimental, low-definition TV broadcast; and in the US, the Bell Telephone Laboratories transmitted a television image in colour between Washington and New York, using three separate channels to transmit the lightprimaries, red, green and blue. In 1932, Zworykin, now at RCA, supervised the installation of television equipment in their flagship NBC studios in the Empire State Building, and in 1935, RCA’s president, David Sarnoff, announced that they would spend a million dollars for TV programme demonstrations. Also in 1935, a station in Berlin began low-definition broadcasting, and in 1936 the BBC began the world’s first high-definition TV broadcasting service. In 1937 a mobile TV unit roved the streets of New York City for live pickups. The pre-war development of television technology culminated in the conception of the shadow-mask colour tube in 1938 by W.Flechsig in Germany, and the invention of the first large-screen television projector, Eidophor, by Professor Fischer at the Swiss Federal Institute of Technology in 1939. PART FOUR: COMMUNICATION AND CALCULATION 746 The year 1939 also saw the opening of the New York World’s Fair, at which Sarnoff premiered commercial television. RCA also demonstrated a complete home TV set; a peculiarity of this set was that viewers did not look directly into the CRT, but saw the tiny images in a mirror—whether this was done because of concern about irradiating the public, or for technical reasons is not known. A few of these sets were sold to enthusiasts; others, more technically minded, built their own to receive the experimental broadcasts, but the war delayed regular television broadcasting. Television broadcasting After the war ended in 1945, the US Federal Communications Commission (FCC) resumed television licensing, displacing FM radio’s allocation in the frequency spectrum. By mid-1946, 24 new licenses had been issued. The Columbia Broadcasting System (CBS), long RCA’s main rival, demonstrated a colour system invented by Peter Goldmark. Although giving a brilliant image, it was incompatible with the existing black-and-white sets which RCA had just placed on the market. Therefore, RCA wanted to delay approval, and in 1947 the FCC postponed any colour decision. It was not until 1953 that the FCC adopted a compatible colour system, called NTSC (National Television Systems Committee). In 1956 an improved system called SECAM (Sequentiel Couleur à Memoire) was devised in France; and in 1962, PAL (Phase Alternance Line) appeared in Germany. All these systems are incompatible, and in consequence no world-wide television system is possible without conversion until a new, high- definition, all-digital replacement is introduced, probably in the 1990s. In the US, 1947–8 saw the beginning of television entertainment as well as news, pitting NEC and CBS against each other for the flood of advertising revenue. In 1949 the first TV set to appear in Sears, Roebuck’s mail-order catalogue was offered for $149.95. By 1956–7, 40 million (85 per cent) of all US homes had TV sets; there were 500 TV stations; and families were spending five hours a day before the ‘tube’. Advertisers flocked to take advantage of the immense persuasive power of the medium, even experimenting with such Orwellian devices as subliminal perception. In 1962, the first transatlantic television transmission was achieved, using the communications satellite Telstar I (see below). COMMUNICATIONS SATELLITES The basic principle under which satellites function is due to Kepler, who first elucidated the laws under which planets orbit the sun (celestial mechanics). INFORMATION 747 However, the notion of an artificial satellite was apparently first conceived in an 1870 science-fiction story, The Brick Moon by Edward Everett Hale. The story featured the use of a visible, 60m (200ft) diameter body orbiting the earth to assist navigators. In 1870, Asaph Hall discovered two natural satellites revolving around Mars, and told Hale that from what he could see, one might be such a ‘brick moon’. Jules Verne’s novel From the Earth to the Moon (1865) was remarkably prophetic, not in the mechanism used—a train-like projectile shot out of a huge cannon—but in his choice of geographical locations. Verne picked Florida for his launch site (a hundred years later, the first manned moon rocket left from Cape Canavaral), and the cannon was designed in Baltimore (home of the Glenn L.Martin company, which built the Viking rocket, an early improvement to the Second World War V2). However, it was not until 1924 that Hermann Oberth described the potential advantages of artificial satellites in detail, including space stations and huge space mirrors to control weather, in his book Wege zur Raumschiffahrt (‘Ways to Space flight’). After the Second World War serious work on artificial satellites accelerated. In 1945, Arthur C.Clarke published his prophetic article on the advantages of a geostationary orbit for satellites to be used for radio and television communications. Wernher von Braun published in 1952 a popular article advocating the use of a manned space station for military purposes. Other, more peaceoriented proponents wanted small, instrument-carrying satellites for scientific purposes (see Chapter 13). The first satellite designed specifically for communications was launched in 1960. Dubbed ECHO 1, it was nothing but a huge reflecting sphere for relaying voice and television signals. However, it was soon followed by the first active repeater satellite, Courier 1B, and the communications satellite era began in earnest. In 1962, Telstar I became the first communication satellite which could relay not only on data and voice, but also TV. Although NASA, a US government agency, provided the launch, a private corporation, AT&T, owned the satellite; a few months later, Congress authorized the creation of COMSAT (Communications Satellite Corporation) as a private corporation. In 1963, the first satellites to be placed in geosynchronous orbit—with all the advantages that Clarke had foreseen—were launched. These, the Syncom series, were built by the Hughes Aircraft Corporation. Because their on-board power was low, and because the Syncoms had to be placed in an orbit 37,000 km (23,000 miles) from the earth’s surface, ground stations had to employ 30m (100ft) diameter parabolic antennas (called ‘dishes’ from their appearance), which cost $3–5 million each. In 1959, Clarke, again foreseeing the next step, published a popular article advocating satellites of great power, whose signals could be received by low-cost antennas connected to ordinary TV sets; in the late 1980s, several such direct-broadcast satellites (DBS) have been put into orbit. PART FOUR: COMMUNICATION AND CALCULATION 748 From 1960 thousands of satellites were launched by the US and the USSR for a variety of military and civilian purposes; and by them for other countries. The West, under the multinational consortium Intelsat, preferred geostationary orbits for its communications satellites, three of which are enough to provide world-wide coverage. The East, under Intersputnik, preferred close-in, nearpolar orbits, although this means that many satellites are required to provide 24-hour coverage; also, they must be continuously tracked as they flash from horizon to horizon. However, much less power is needed aboard, and smaller earth-station antennas can be employed. The launch monopoly held by the two superpowers has been challenged since 1979 by the European Space Agency (ESA), using their Ariane rocket, and other countries including China and India have the capability. Also, these countries and Japan have built their own satellites. In the 1980s, the US became more and more dependent on NASA’s manned space shuttles for satellite placement, but a launch disaster in 1986 gave new impetus to conventional rockets. Back to ‘wire’? By the mid-1980s, Intelsat had so many satellite circuits available over the north Atlantic for telephone, data and television transmission that it had surplus capacity. Furthermore, a rival technology, transatlantic fibre-optic cables, was threatening satellites with severe competition. Laser beams, travelling in two pairs of glass fibres, are capable of carrying the equivalent of 37,800 simultaneous telephone conversations. Even greater capacity is in the offing, AT&T’s Bell Laboratories having achieved a record of 20 Gbits (1 gigabit= 10 9 bits) per second over one hair-thin fibre using optical multiplexing, the equivalent of 300,000 conversations. The idea of beaming TV programmes directly into homes by means of very high-power direct broadcast satellites (DBS) is being challenged by co-axial and hybrid fibre-coax distribution systems. Thus, we may come full circle, back to the original concepts of telegraphy—a ‘wired world’, rather than one principally dependent upon space technology. INFORMATION STORAGE TODAY In principle, any physical phenomenon can be used for recording information, but until the scientific revolution information always remained readable by the naked eye. Only after optical (photographic), electromechanical (telegraphic and phonographic) and magnetic recording methods were developed did we extend our storage capacities to the submicroscopic level. INFORMATION 749 Also, with the exception of telegraphy, information was recorded in analogue form. The alternative, digital recording, is much simpler in principle: finger-counting and tally sticks were among the earliest digital techniques. The development of the electric telegraph, which used a pulse-code system from the beginning, led to theoretical studies of digital systems and analogue-digital conversion technologies. Digital systems for data storage are only two centuries old. However, the inventions of Jacquard, Babbage and Hollerith (see pp. 699, 701) were mechanical, and even when they became electromechanical they were relatively slow in operation. The acceleration of science and technological development during the Second World War provided practical electronic, magnetic and optical data storage systems. Pulse-code modulation and information theory In 1926, Paul M.Rainey of the United States was granted a patent on a pulse coding system, but nothing seems to have come of it until Alec H.Reeves, an Englishman working in the Paris laboratories of the International Telephone and Telegraph Company (ITT) reinvented it in 1937; the fundamental PCM (Pulse Code Modulation) patents were granted to him in 1938 and 1942. However, no available electronic components were capable of implementing PCM at a reasonable cost. During the Second World War a team headed by Harold S. Black at the Bell Telephone Laboratories designed the first practical PCM system for the US Army Signal Corps to safeguard telephone conversations. Civilian applications had to wait until relatively recently, when semiconductor technology—particularly the integrated circuit (see p. 705) —made them economically attractive. The first significant PCM application was in digitizing voice communications for telephony. For PCM, soundwave amplitude is sampled 8000 times every second and each sample encoded to a 7-bit accuracy (1 part in 128), with an extra bit added for signalling purposes. Thus 64,000 pulses per second (64 kbits per second in today’s units) are necessary for intelligible speech transmission. In 1948, Claude E.Shannon of the Bell Telephone Laboratories published a seminal paper, ‘The Mathematical Theory of Communication’, which for the first time provided a sound theoretical basis for understanding information and communication phenomena of all kinds. He outlined a ‘universal’ communication system: a source, producing messages; a transmitter, encoding them into suitable signals for transmission; a channel, through which the signals travel; a receiver, decoding the signals; and a message destination. Sender and receiver are usually human beings, the other elements being mechanical, optical, electronic or other artificial means. Another element, a source of noise, PART FOUR: COMMUNICATION AND CALCULATION 750 is always present in real communications channels. This general model applies from the simplest to the most complex communication systems. Another part of Shannon’s theory gives a precise measure of information, based on the concept of uncertainty (entropy in thermodynamics; information has been called negentropy by some information theorists). A bit (a neologism formed from ‘binary’ and ‘digit’) can represent the uncertainty between ‘yes’ and ‘no’ when both are equally likely; the message content, the storage capacity, the transmission rate, and the channel capacity can all be measured in terms of bits. For example, a telephone channel which has a band-width of 3000Hz has a channel capacity of about 60,000 bits per second, and commercial television, with a 6MHz band-width, requires a channel capacity approaching 100 Mbits per second—more than a thousand times greater. The work of Reeves, Shannon and many others will culminate in a totally digital switched public telecommunications system known as ISDN (Integrated Services Digital Network), which will replace the existing analogue networks which have been the only public carriers for more than a century. ISDN will transmit voice, data, text and images using multiple 64kbit-persecond channels. Image and data storage and retrieval systems Starting in the 1950s, many attempts have been made to use electromechanical—essentially phonographic—techniques to store and play back images, such as Phonovid, a still-picture TV system (Westinghouse, mid- 1960s); and Teldec, a full-motion, black-and-white TV system (AEG- Telefunken and Decca, 1970). They failed: Phonovid required an expensive scan converter; and Teldec, even though attaining a storage density 100 times greater than that of LP records, could only play 7-to 15-minute programmes. About 1970, EG&G Inc. introduced their Dataplatter, an adaptation of 7in (18cm) diameter, 45rpm phonograph technology which could store up to 5 megabits (Mb) of data. The reasons for the failure of this innovative technology in the marketplace are unclear—perhaps it was too far ahead of its time, coming five years before the microcomputer. Optical means have been used almost from the invention of photography, but only for images, not for digital data. However, in 1945, Vannevar Bush published a seminal article, ‘As We May Think’, in a popular American magazine, the Atlantic Monthly. Bush had developed the Differential Analyzer in 1931, one of the earliest analogue computers, for solving differential equations. During the war he became director of the US Office of Scientific Research and Development. Looking forward to a conversion of the massive wartime scientific effort to peacetime uses, he pointed out how primitive were our methods of accessing the research literature. After predicting the inventions of dry photography, ultramicrofiche and the voice-operated typewriter, he INFORMATION 751 conceived an automatic system for the mass storage and rapid retrieval of documentary information, which he called ‘memex’. Memex was based on an extrapolation of imaging technology, but the selection principle was associative indexing, which only now is coming into the realm of the possible as a technique of ‘artificial intelligence’. It was not long after Bush’s detailed prophecy that automatic retrieval of photographically reduced documentary information was embodied in working hardware. The Filmorex system, invented by Jacques Samain in France early in the 1950s, used 70×45mm (23/4×13/4in) film-cards (or microfiche, which French word has been adopted into English). Each Filmorex fiche contained two moderately reduced page images, together with a grid of tiny squares on which was encoded up to 500 bits of index information. When the fiche passed by an array of photocells in the Filmorex selector, code-combinations matching the search request would trip a release mechanism and divert the selected fiche to a bin for viewing. A similar system, Minicard, was developed in the 1950s by Kodak’s Recordak Division. This was based on tiny fiche cut from 16mm microfilm, each of which could store up to six pages at a 60:1 reduction, together with more than 1500 bits of data. Roll microfilm was used for optical data storage in FOSDIC (Film Optical Scanning Device for Input to Computers) to speed up the processing of the vast amount of data collected for the 1960 US census; data were reduced images of punched cards, compressed vertically by photographing them through an anamorphic lens. Videotape In 1956, Alexander M.Poniatoff demonstrated the first videotape recording (VTR) device; and in 1958 his Ampex Corporation installed the first VTR in American television studios. This invention radically changed TV programme production and dissemination. The first VTR machines used 2 inch-wide (5cm) tape and were very expensive, but programmes could be recorded and played back immediately, unlike film; this capability was of incalculable value for television production. The public could no longer tell whether it was watching a programme ‘live’ or ‘canned’. Attempts had been made to store television on tape before, but these had been brute force systems based on tape speeds hundreds of times greater than used for audio—with concomitant mechanical problems. Poniatoff saw that the required megahertz band-width could be achieved without these penalties by using magnetic heads rotating at right angles to the linear tape motion. Ampex also realized that VTR technology could store high-resolution still images. In the 1960s they marketed Videofile, which could store facsimiles of 250,000 pages (about 5Gbits: 1 gigabit=10 9 bits) on a reel of videotape. These systems cost several million dollars and only a few were purchased by government agencies and . orbit. PART FOUR: COMMUNICATION AND CALCULATION 748 From 1960 thousands of satellites were launched by the US and the USSR for a variety of military and civilian purposes; and by them for other. later, the first manned moon rocket left from Cape Canavaral), and the cannon was designed in Baltimore (home of the Glenn L.Martin company, which built the Viking rocket, an early improvement to the. character sets of their language. They now have a virtual monopoly on the manufacture of facsimile machines, which are capable of unattended transmission and reception at speeds of less than a minute