THE HONGKONG TELEGRAPH. FRIDAY,^ APRIL
1935.
EXPLAINING MARVEL OF TELEVISION
SAVANT TELLS OF EYES AND EARS OF SCIENCE®
By CAPTAIN ERNEST H. ROBINSON Television brings into the home moving pictures of events happening at a distance in much the same way, as broadcasting brings to our firesides sounds which are produced at long range. The production of televised pictures is a complicated and dicult business, and that is the reason why it is not as advanced as sound broadcasting. Its main principles are, however, quite easy to understand.
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If a stone is thrown into a still pond, ripples start from the point where the stone entered the water and radiate out along the Burface in all directions. A cork, u twig, or a duck at some dis- tance from the splash of the stone will begin to bob up and down, when the waveleta arrive. That is a simple Illustration of a transmitter and receiver. The stone in motion jerked the water, the jerk act up waves, which moved the duck, twig, or cork ten or fifteen feet away-·.
ting of one wave on top of another is called "modulating," and the instrument which picks up the flow of jerks is known as the micro- phone. The way in which the sound jerks are turned into elec |trical activities and then rulxed up with the other electrical agitations which are continuously going out from the acrint is a somewhat com- plicated business, but may be set
which
When wo speak, ring a bell, or strike a piano wire, a jerk is given to the air and waves are set up which go out la all directions. The most usual receiver in the came of sound waves is the car, but they can be detected in other ways. For instance, if there are two tuning forks of exactly tho same pitch and one is struck, the ather, six inches or a foot away, can be seen, hoard, and felt to beside for the moment. That, how- vibrating.
When we strike a match or switch on the electric light we start waves of another sort, for which the receiver is the eye. These waves are not in the air be- cause, in the case of the electric light bulb, they may start where there is no air at all. Also light waven come to us from the sun and are very similar to wireless waves. They travel at the anme speed, 180,000 miles a second, and belong to a huge family of similar activities.
Waves are always started by Home kind of a jerk. To keep them going out continuously the necessary jerk must be constantly repeated. For example, if you pluck a violin atring you hear one short, sharp sound which quickly dies away. The same note made by drawing the bow across string will persist as long as the how is in motion. In like mauner continuona jerks are set up in the minute particles of the aerial. These jerks start waves which, when they arrive at another aerial, repoat themselves,
the
Suppose a boat is taken out to the middle of a pond and some big waves are started by drop ping a heavy stone overboard following the action directly after- wards by throwing in a smaller stone. The result will be that two separate motions are launched -the Blow action of the long waves and the short sharp effect of the small ones. The ripples become mixed up, so the cork or -ether object on-the-surface-moves-
with a wobble on a wobble.
"MODULATING.”
Exactly the same sort of thing is done in broadcasting. The first continuous Wave which went out is followed by another series. The broadcasting parlance for the put-
Lever, is the principle on
broadcasting is done.
Now comes the turn of the re- calving set. The wireless waves on hitting the aerial start the minute particles in the copper] jumping about in sympathy, and the valves and other parts in our! receiving set sort out the two dif-i Terent. kinds of wave and pass those started by sound on to thei loudspeaker, which Jerks the air of the room, setting up sound waves which our cars receive.
The sending and receiving of pictures is a trille more compli- cated. In no known way at pre- nent can the whole picture be sent at once. The scene has to be divided into small portions and each bit despatched separately.
Take an example. A girl is standing singing with her back to ja screen. The sending apparatus
starting at the top corner of the! screen looks along a small strip.
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The Prince of Wales distributing medals to officers' of the Walsh Guards in London recently,
OBTAINABLE AT
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18 Hankow Road,
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When it has reached the opposite A street performance of scenes from "The Old Curiosity Shop," one of Dickens" måsterpieces, draw a crowd at
corner it returns swiftly and
sturte to look along the next strip
24
little lower down, and this pro- ceas is continued until the whole of the picture is completed. This In called "scanning" and the effect is that a whole series of jerks is started whether they are big or little depends on whether the pic-} ture is light or dark. These are mixed with the continuous wave of |the transmitler just as is done! with the sound wayes in ordinary broadcasting
| THE RECEIVING END
The receiving end is provided with a machine which sorts out the waves representing the picture jand then they have to be repro- diced hit by bit just as they were originally composed and sent out. The action, however, takes place (so quickly that It conveys the im- pression of being a complete pic- ture. Each phase of recoption is depicted so rapidly that, as in the Jeuse of the film, the presentation Jappears whole and unbroken.
As has already been explained, both sound and fight are conveyed over a distance by waves. Sound
Is a succession of ripples in the air, and light lo a succession of movements in another medium. which is conveniently referred to an the "Ether." As a matter of fact our only ovidence that the Ether exists is the fact that light | waves and wireless waves travel!
through space.
Within the last ten years anime.
Southwark, London.
Underwater battler with Florida alligators are looked upon as "sport" in the Everglados.
London will have any service, and be to the advantage of both par-
efficient kind of electric eye has There are several ways of con- that will not be for more than tiss. been developed. In shape it is trolling this light, and as many about two hours each evening, There is one possibility with much like an electric light bulb systems of television. Which will The cinema industry has viewed regard to the cinema which must or wireless valve It works by ultimately prevail-remains-to-be-with-some-consideration the pro-not be overlooked, and that is the turning light waves into electric determined.
gress of television, just as the setting up of central transmitting Impulses. This small electric eye
gramophone industry was per stations to serve groups of cinoma:
Lalkles and television.
has made possible the cinoma For the next few years tele- turbed by the coming of broad- theatres within an area of, say. vision can be nothing but a toy casting. Ultimately, no doubt, the twenty miles. At present, how- At the transmitting end in a and for a year or two.a.tos of the film industry will be closely as ever, the cost of the sending of Japan take a walk along a Tokyo television systera we have a viewer comparatively well-to-do. In any sociated with television. The two stations and the receiving appata- which looks at the picture to be case, for a good many montha things are obvious partners. The tus would be too great to displace sent, a spot at a time, just as we after the first programmes are coming together must, however, the present nim distribution sys- read a page in a book a letter at a,sont out only those dwelling round, be a gradual process and should tem.
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