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 Brésides sounds which are produced at long range. The production of televised pictures is a complicated and <lifficult business, and that is the reason why it is not as advanced as sound broadcasting. Its main principles are, however, quite. easy to understand.
If stone is thrown into a still pond, ripples start from the point where the stone entered the water and radiate out along the surface in all directions. A cork, a twig, or a duck at some dia- tance from the splash of the stone will begin to bob up and down when the wavelets arrive. That la simple illustration of a transmitter and receiver. The stone in motion jerked the water, the jerk set up waves, which moved the duck, twig, or cork ten or Afteen feet away.
When we speak, ring a bell, ar strike a piano wire, a jerk is given to the air and waves are set up which go out in all directions. The most usual receiver in the case of sound waven is the car, but they can be detected in other ways. For instance. If there are Two Luning forks of exactly the same pitch and one is struck, the other, six inches or a foot away, wan he seen, heurd, and 'Telt to be
vibrating.
match
When we strike switch on the electric light we start waves of another sort, for which the receiver is the eye. Theas waves are not in the air be- enune, in the case of the electric light bulb, they may start where there is no air at all. Also light waves come to us from the sun and are very similar to wireless waves. They travel at the Kamie speed, 186,000 miles a second, and belong to a huge family of almitor activities,
Waves are always started by some kind of a jerk, To keep them going out continuously the necessary jark must be constantly repeated. For example, if you pluck a violin string you hear one short, sharp sound which quickly
ies away.
The same note made
by drawing the bow across the string will persist na long on the how in motion. In like manner continuous jerks are set up in the minute particles of the aerial. These jerks start wares which, when they arrive nt another aerial, repeat themselves.
Suppose a boat la taken out të the middle of a pond and sume big waves are started by drop ping a heavy stone overboard following the action directly after- warda by throwing in. a smaller stone. The result will be that two separate motions are launched -the slow action of the long waves and the short sharp effect of the small ones. The ripples become nuxed up, so the cork or other 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 is sent out is followed by another serles. The broadcasting parlance for the put-
Youthful "Admiral" and "General"
ting of one wave on top of another is called "modulating," and the instrument which pleks up the flow! of jerks is known as the micro-l phone, The way in which the sound jerks are turned intá alec. trical activities and then mixed up with the other electrical agitations: which are continuously going out from the aerial Is a somewhat.com- pilented business, but may be aut aside for the moment. That, how- fever, is the principle <271 whleh
breaitcasting is done.
Now comes the turn of the re- reiving 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- ferent kinds of wave and pas those started by sound on to the loudspeaker, which jerks the alr fof the room, setting up sound
waves which our cars receive.
The sending and receiving of pictures 1s a trifle more compli cated In-no, known way at pre-i sent can the whole picture be sent) fat once. The scene has to bet divided into small portions und euch bit despatched separately.
Take an example. A girl is |standing singing with her back to in screen. The sending apparatus] starting at the top corner of the sereen looks along a small strip.) When it has reached the opposite corner it returns swiftly and starts to look along the next strip a little lower down, and this pro- cess is continued until the whole of the picture is completed. This
is that a whole series of jerks in is valled "scanning" and the effect startet whether they are big or little depends on whether the pie tare is light or dark. These are mixed with the continuous wave of the transmitter' just as is done with the sound waves in ordinary, breadcasting.
THE RECEIVING END
The receiving end is provided with a machine which sorts out the waves representing the picture ; and then they have to be repro- duced bit 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 pie! ture, Each phase of reception is depicted as rapidly that, as in the ease of the film, the presentation appears whole and unbroken.
As has already been explained, both sound and light are conveyed j over a distance by waves. Sound] Is a succession of ripples in the fair, and light is a succession of movements in another medium which is conveniently referred to as the "Ether." As a matter of fact our only evidence that the Ether exists is the fact that lighti waves and wirelens waves travel through space.
THE HONGKONG. TELEGRAPH. FRIDAY, APRIL 5, 1985.
The Prince of Wales distributing madals to officers of the Welsh Guards In London recently.
A street performance of scenes from "The Old Curiosity Shop," one of Dickens' masterpieces, drew a crowd at Southwark, London.
Within the last ten years an time. efficient kind of electric eye has
Underwater battles with Florida alligators are looked upon as "sport" in the Everglades.
Lonilon will have any service, and be to the advantage of both par There are several ways of con- that will not be for more than ties, been developed. In shape it is trolling this light, and as, many about two hours each evening. much like an electric light bulb systems of television. Which will
There is one possibility with or wireless valve. It works by ultimately prevail remains to be with some consideration the pro- not be overlooked, and that is the The cinema-industry hna viewed regard to the cinema which must turning light waves into electric, determined.
impulses. This small electric eye)
gress of television, just as the setting up of central transmitting, haa mnde possible the cluema
For the next few years tole- gramophone industry was per- stations to serve groups of cinema talkies and television.
vision can be nothing but a toy, casting. Ultimately, no doubt, the twenty miles. At present, how turbed by the coming of broad- theatres within an area of, say, of Japan take a walk along Tokyo television system we have a viewer comparatively well-to-do. In any sociated with television. The two stations and the receiving appara- At the transmitting end in a and for a year or two a toy of the nim industry will be closely as ever, the cost of the sending which looks at the picture to be case, for a good many months things are obvious partners. The tus would be too great to displace sont, a spot at a time, just as we after the first programmes read a page in a book a letter at a, sent out only those dwelling round be a gradual process and should tem."
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