John Logie Baird
In 1925, an electrical engineer from Scotland, John Logie Baird, exhibited in Selfridges department store in London an apparatus with which he reproduced a simple image, in fact white letters on a black background, at a distance. It was not really television because the two discs which served to transmit the image and to reproduce it, were mounted on the same shaft. However Baird did effectively demonstrate that the principle of successive scanning could be applied in practice. He did it again in 1926, in his laboratory, with the first transmission of a real scene the head of a person. The picture was scanned in 30 lines, with 5 full pictures every second.
TELEVISION IN 1932
By J. L. BAIRD, Managing Director of Baird Television, Ltd.
TELEVISION IN 1932 By J. L. BAIRD, Managing Director of Baird Television, Ltd.
No one will gainsay that the year 1932 has proved to be a most important landmark in the development of this newest of sciences-television.
After nearly three years of experimental transmissions emanating from the Baird Studios in Long Acre and broadcast by the London Regional transmitter of the B.B.C., a sufficient degree of advancement has been made to justify the B.B.C. taking over the studio side of the work. In my opinion this constitutes the most important step which has yet been taken towards the realizing of proper commercialization and the introduction of television to the public at large.
It may come as a surprise to many to learn that as far back as 1926 television transmissions were broadcast by the B.B.C. These, however, were of an entirely experimental nature and were received only on our own machines; for apparatus at that date was not in the hands of the public. From these crude beginnings we were able to establish that television could be broadcast successfully by the B.B.C. transmitters, and from that date a steady progress commenced.
Negotiations with the B.B.C., which took place over a rather lengthy period, culminated in September 1929, when the first official broadcast of television was made through the new London Regional Station at Brookmans Park. A spirit of friendly collaboration was established and considerable technical knowledge of this important side of television has been acquired.
Steady progress then commenced, one of the results of which was the broadcasting of the play "The Man with the Flower in his Mouth" which was due to the united efforts of'-Mir. Sydney A. Moseley, Mr. Val Gielgud, and Mr. Lance Sieveking.
Another landmark in television progress was reached in June 1931, when a view of the winning post at the Derby was broadcast. This was repeated in 1932.
The most valuable result of the years of experimental broadcasting which have been gone through has been the acquiring of a vast amount of technical experience. I feel, now that the B.B.C. has taken over the programmes and transmissions, advancement will be most rapid and the public can look forward to television programmes of sustained entertainment value.
In spite of the large amount of information which has been disseminated on the subject of television, I find that the majority of the general public are still in complete ignorance of what television means and how the process is effected.
In the space at my disposal, therefore, I propose briefly to outline both the transmitting and receiving sides of the problem.
First of all we mean by television the process of being able to see, through the medium of electrical methods of transmission, the reproduction of images of living, moving, or stationary objects which are at some distance from the observer. It can really be looked upon as the reproduction of sight, for it is possible to witness visually what is happening at some distance just as if we were eye-witnesses on the spot.
Corning to the process itself, the subjects to be televised are positioned in front of a Baird spot-light transmitter - and explored by a rapidly moving spot of light. For the purpose of explanation let us assume we are televising the head and shoulders of an artist. In front of him is a powerful source of light which is broken up mechanically into a rapidly moving spot. This is effected by having a beam of light projected on to a revolving drum around whose outer edge are positioned mirrors,' each one set at a slightly different angle to its predecessor. The effect is to cause a tiny area of light to move from the button to the top of the subject's features and thus create a strip of light. Immediately this one spot has finished its movement, a second spot takes its place and performs an identical movement, except that this second strip is displaced to the left of the original strip. In this way 30 strips of light are built up side by side, each strip just touching its neighbour on either side, and although at any one instant only a tiny spot is visible, the process is carried out so rapidly, namely, 12 1/2 times per second, that an onlooker would have the impression that the artist was completely illuminated.
A bank of photo-electric cells is placed in front of the artist, and this "
television eye " follows the movement of the spot of light and picks up
that amount of light which is reflected from the spot playing on
the subject being televised. A corresponding current variation is then produced
in the cell circuit, and at the next instant, when the spot has moved to its
adjoining position in the light strip, a different amount of light is reflected
and the cells respond accordingly.
In this simple way the scene is analyzed, and the television signals arc made to modulate the carrier-wave sent out by the broadcasting station and are transmitted through space as ordinary wireless signals. These can be detected and received in the normal manner by anyone possessing a wireless receiver. If, however, the individual tuned in vision radio signals and passed them on to a loudspeaker, he would be rewarded with a peculiar note which makes no pretence at being musical. On the other hand, if the signals from the output circuit of the wireless receiver are passed to a "Televisor receiver," then the result will be an intelligible image which, in effect, is a replica in miniature of the artist in the television broadcasting studio.
The vision-receiving apparatus, in order to bring this about, must consist of a source of illumination, the intensity of whose light can be made to fluctuate in exact conformation to the variations which originally take place in the photo-electric circuit at the transmitting end. In the original disc model machine this source of illumination was a flat plate neon lamp whose large electrode glowed brightly or darkly according to the signal strength which was made to modulate it.
In the new model machine, however, this neon lamp has been replaced by a projection lamp whose beam of light is now modulated by being passed through Nicol prisms and a glass cell filled with nitro-benzene, in which plates, similarly arranged to accumulator plates, are immersed. These plates are connected to the output of the wireless receiver, and as the voltage varies, the light passed by the cell varies in unison. This grid cell is a modification of the cell used many years ago by the physicist Kerr in his experiments with polarized light, but the use of grids in place of simple plates enables a low voltage to be employed and renders the device practical. The beam of light modulated by the grid cell is projected on to a revolving mirror drum, and this in turn is reflected on to a translucent screen positioned in front of the drum. Since the whole process is effected at a speed of 12 1/2 times per second, the characteristic lag or persistence of vision of the eye interprets this as a continuous movement, in much the same way as the still pictures projected on to a screen at an ordinary cinema are built up into the continuous and apparently unbroken movement owing to this same property of the eye.
In Germany, Fernseh A.G., a combination of the Baird Company, the Zeiss Ikon Optical Company, the Bosch Magneto Company, and the Loewe Radio Company, which was formed. in 1929 to develop our system of television, has supplied a transmitter to the German Post Office which is very similar to that used by the B.B.C., and television in Germany is developing along parallel lines to developments in this country and we work in the closest collaboration. A similar state of affairs exists in France, where Television Baird- Nathan is using the wireless station P.T.T. on the outskirts of Paris for the experimental broadcast of television, and we are now constructing a transmitter for them on the same lines as that being used in Broadcasting House. In the United States of America extensive work is being done with television by the members of the huge combine known as the Radio Trust, and in addition numerous broadcasting stations are sending out television transmissions similar to those in Europe. The Baird Company of England has an affiliated, Company in America, and last year W.M.C.A., one of the large broadcasting organizations of New York, arranged to take up the British system for broadcasting television, in preference to any American system offered them. An agreement was fixed with them, but the British Company was refused permission to broadcast in America by the Federal Radio Commission on the grounds that-to quote one of the leading technical journals:
". . . although the application was made in the name of W.M.C.A., an American Company, the proposed station would be operated jointly with Baird Television Corporation, Ltd., a British concern. According to the Commission, the granting of a license would, in effect, give undue authority to the British Company in violation of the section of the Radio Law prohibiting alien ownership or directorates of companies holding wavelength privileges in the United States."
It might be advantageous to our "Buy British" policy if this country were to adopt a similar attitude towards Amenican controlled concerns.
TELEVISION FOR THE CINEMA
The application of television to the cinema and places of public entertainment involves the use of a large screen, and considerable development work has been done in this direction. The broadcasting of the play "The Man with the Flower in his Mouth" was not only shown on the ordinary "Televisor" receivers but was also shown to a large audience on the roof of the Baird Long Acre premises on a screen 2 feet by 5 feet, and the same screen was shown in Paris, Berlin, and Stockholm; but while it attracted large audiences, the pictures could not in any way compare with the cinematograph, and the attraction was one of novelty. Since that time the screen has been so far developed that it is now approaching the perfection necessary to give full entertainment value apart from the curiosity attraction, and I believe that one of the largest fields for television lies in the cinema of the future.
John Logie Baird ---------------------- See: HISTORY OF TELEVISION
|His system was crude by
modern standards comprising only 30 lines per picture. The low resolution
drove him to 'tune' the scanning direction and aspect ratio to be a
vertically-scanned letter-box. This would allow the best match for
The years from 1927-1929 were Baird's most innovative. He experimented with all aspects of this new form of communications. These experiments made him a legend in his own lifetime. His mechanical approach allowed him to try out ideas that would not be possible in the electronic systems for many years to come. In fact, colour television, stereoscopic television and television by infra-red light were all demonstrated by Baird before 1930. His transmission of the image of a face across the Atlantic in 1928 was epoch-breaking, but as it was never repeated or developed further, it is merely a demonstration.
He successfully lobbied for broadcast time on the BBC. The BBC started broadcasting television on the Baird 30-line system experimentally from 1929. The first simultaneous sound and vision play was broadcast in 1930. In July 1930, the first British Television Play was transmitted - "The Man with the Flower in his Mouth".
The BBC adopted Baird's 30-line system in 1932 - despite higher resolution systems being available. By 1932, the 30-line system was mature and exceptionally low-cost in engineering terms - the BBC could use their existing audio transmitters for the low-bandwidth video. But it wasn't just the cost of the service, there were no suitable wide-band transmitters readily available for developing a service and there was no infrastructure that could be rolled out to the public in such a short while. Transmissions on the BBC continued until 11th September 1935 as developments in fully electronic television led to the demise of the 30-line service. It was replaced with the world's first regular high-resolution (405 lines per picture) television service by the BBC in 1936.
Where's the evidence of Baird's Achievements?
HISTORY OF TELEVISION
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