Projection engineering (Sept 1929-Nov 1930)

Page 22 Projection Engineering, September, 1929 D. V. Mihaly, the inventor of a European televisor of simplified design. Note the horizontal scanning disc under which is the synchronizing mechanism. so that an image can be broken down into a large number of sections, each of which may be flashed simultaneously, for maximum detail. Meanwhile, the other school, with very limited radio channels available, must make the most of these channels, handling probably the entire image at one time as at present. Because of the multiplicity of channels, the telephone engineers are essaying pictures with considerable detail, and even colored pictures through the use of color filters and color screens, with multiple images for the different primary color values. All of which is quite feasible with unlimited channels of highest efficiency. Television for the Home The school in which the radio industry must take the keenest interest, even if its work appears so crude just now, is that school endeavoring to evolve something commercial out of television. This school is working on images with 24 lines, 48 lines and 60 lines. The last-mentioned screen appears most desirable at present, for it includes a remarkable amount of detail and is certainly a marked improvement over the 48-line picture, although this point is violently contested by workers in the 48-line field. Nevertheless, on the basis of sheer logic, it stands to reason that an increase of one-third in the fineness of texture must produce a noticeable improvement in detail, everything else being equal. One point generally overlooked in considering television images is the part.played by the human imagination. A somewhat far-fetched comparison will serve to make this point clear. When we read words, we do not read and sound out each letter, so as to identify the words themselves. Instead, through long practice, we read purely by the general appearance of each word. This is called reading by context or general outline. Even if a letter is missing, we read the word just the same. The best proof of this is in proof-reading, where missing letters are often overlooked even by the trained eye. Much the same applies in present-day television. While our images for the present are little more than figurative short-hand images, our eyes and our imagination supply the missing details to a remarkable degree. By context, if you please, we secure a pleasing image even with 48 lines. One must see the television images for one's self in order to appreciate the role played by our imagination. Therefore, we predict that 48 lines will be sufficient to begin with, although 60 will be more desirable. Furthermore, by the development of a satisfactory television technique in the way of prominent detail, a postery treatment of lights and shadows, properly timed action and so on, the utmost can be made of presentday limitations. When we compare the 48-line picture of television with the 48-line half-tone of the printed picture, the comparison is really far-fetched. We are dealing with two totally different things, and the 48-line television picture is as detailed as the 80-line screen half-tone, because of the part played by lights and shadows, better context, and the keener imagination of the looker-in. AVhat is meant by something commercial, as applied to television? Well, we want a televisor, or picture miscrambler, which can be sold for say $200.00 or less. The associated equipment in the form of short-wave receiver and amplifier, naturally increases the cost considerably. Later, we hope to drop the price from $200.00 to even $60. It probably can be done through mass production, although the synchronous motor now employed must always remain a big item of cost, unless it can be replaced by a less costly synchronizing means. The televisor must be so simple that it can be operated by the same person who now operates a broadcast receiver. The television signals must be received over a reasonable distance, without excessive regeneration or other means likely to introduce distortion, and properly reproduced. The synchronizing means must be reduced to simplest terms. The picture must be viewed by a group rather than by a single person. Silhouette Radiomovies All the foregoing requirements are being met in commercial televisors shortly to be placed on the market. Of course the pictures are going to be relatively simple, and we even dare predict that they will be, for the most part, silhouette radiomovies, although the same televisors will handle silhouettes or half-tone without change or adjustment of any kind. Silhouettes, or plain black-and-white signals, are simpler to handle, especially over the considerable ranges which must be covered by the handful of television transmitters with which slight broadcasting must inaugurate its regular service. It is often argued that the simple silhouette radiomovies will not have sufficient appeal. Here, we believe, the persons presenting the arguments are decidedly short on memory. It is not so long ago that sound broadcasting was woefully deficient. In transmitting organ selections, for instance, we were cutting off at about 200 cycles or over, at the low end of the frequency scale, and probably 3000 cycles at the high end. The result was a miserable reproduction, which sounded no more like an organ than a newborn babe trying to initate a basso. Yet at the time the novelty of sound broadcasting quite overshadowed all considerations of tonal beauty. And so it must be with television : the thrill of receiving pictures flashed through space, no matter how crude, will carry the day. The main thing today in television development is to get something into the hands of the public, simultaneously to inaugurate a regular — not an occasional— television broadcasting service, and then to redouble the research and engineering development activities based in large measure on what is learned in everyday practice. All the talk in the world, all the dreaming, all the arguments for or against, are The assembly of televisors by skilled workmen in a well-known television plant. Eventually, the assembly will be by belt conveyors, as in the massproduction plants of radio receivers.