It may come as a surprise to rnany 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
Brookman's 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 Mr. 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 sorne 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
bottorn 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 analysed, 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 polarised 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 organisations of New York,
arranged to take up the British system for broadcasting television, in
preference to any American system offered them. An agreernent 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 licence 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 American controlled concerns.
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.