> > > >

1945 Theatre Catalog, 4th Edition, Page 596 (568)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 596
Page 596

1945 Theatre Catalog, 4th Edition, Page 596

either side of the transmission band.

To explain the vestigial side band transmission, it should be recognized that one side band by itself carries all the characteristics of the signal, no more intelligence is carried on the other band but simply more power. Thus, if advisable, we may partially eliminate one side band, leaving enough of it to avoid certain distortions. This is called vestigial side band transmission and has the advantage that the width of the frequency band required for the channel may be decreased to approximately five-eighths of that required by the ordinary doubleside band method. (Figure 6.)

It has been found desirable to transmit the picture and sound in the same television channel. This permits the use of a single oscillator for both sight and sound in the superheterodyne television receiver, thus greatly simplifying the tuning. In this system, the sight and sound signals are separated by selective circuits in the intermediate frequency amplifiers.

It would be well again to consider the necessity for considering the television receiver as an integral part of an entire system. This is in contrast to sound broadcasting. Television receivers must be designed for transmitters which operate on well-defined standards. If changes are made in these standards, all television receivers might become obsolete or might have to be modified. This is one important reason why so much time and money have so far been spent to develop television to a practical commercial stage before its introduction has been too widespread.

Frequency modulation. the standard

for television sound, is a system for broadcasting which differs from amplitude modulation, in that the frequency of the carrier wave of constant amplitude is modulated or varied by the sound to be transmitted.

The advantages of frequency modulation over amplitude modulation for the transmission of the sound has proved to be so great in terms of clarity, dependability, and economy of transmitting powers that this standard has been adopted. The use of frequency modulation is well adapted to the purpose particularly as ultra-short waves are being used anyway for television transmission.

There undoubtedly will be changes to television standards transmission in the future, but it is safe to say that enough thought and study has been given to the matter of standards by all of the engineers of the industry to permit the widespread introduction and expansion of television.


The ttwhy" of television has been described in as simple language as practical. There have not been very many radical changes in the art of transmitting and receiving since the beginning of the war. While a number of important improvements have no doubt been made to individual parts of the system, not much has been yet said about them. We will now summarize some of the general problems as they now exist with an attempt to forecast certain of the general trends.

One of the most serious problems at

FIGURE 6.-ln "vestigial side band" transmission the partial elimination of one side band is achieved by the use of band-pass filters. Accordingly, only one side band carries all the characteristics of the signal, the other side band carries merely power. Thus, the width of the frequency band required for the channel may be decreased to approximately five-eighths of that which is required when the ordinary double side-band methods are used.






A 3 4- 5



the present time involves a controversy regarding standards. During the past several years new improved vacuum tubes have been designed which make possible the satisfactory transmission of television signals over radio frequencies much higher in the spectrum than have heretofore been used. To adapt television for this new portion of the frequency spectrum would, however in the opinion of many engineers, require a considerable amount of additional development work. >

Most of the companies with television research facilities that have been engaged almost solely in producing electronic equipment for the war effort have just recently been permitted to devote much time to television. The present controversy, therefore, arises around the question as to whether plans should be made for introducing television commercially in this country in accordance with present standards. The exponents of this plan suggest that as television systems utilizing the higher frequencies are perfected a gradual transition should take place so that ultimately all transmitters and receivers would Operate in the higher portion of the frequency spectrum.

The exponents of the other. side of the argument advise delaying introduction of commercial television until the systems have been perfected for use in the higher frequencies. There seems to be considerable differences of opinion as to whether this involves a delay of approximately a year or as much as five years. By following the second plan, it will prevent the introduction and sale of equipment, which might become obsolete within a few years and require costly replacement. Another point, however, is the harm that might arise by delaying for such a long period of time the commercial introduction of television.

One of the interesting phases of this controversy is the fact that those favoring delay are, in general, concerns which have not very much invested at the present time in manufacturing facilities or transmitters and who would, therefore, suffer least by such a delay. Only re cently the Federal Communications Commission, based on recommendations from various groups in the industry, decided to follow the second course.

Summarizing, I think it is safe to say that, from a technical point of view, television has for the most part reached the point where it is ready for commercial introduction. Apparently the perfection of color television is several years 0%. Undoubtedly, ultimately the use of the higher frequencies for television than have heretofore been used will become an accomplished fact. The several commercial problems regarding both home and theatre television will, of course, have to be solved, but it is encouraging to note the progressive interest and activity on the part of many people in the industry to insure the accomplishment of this objective in the not too distant future. It appears certain, as well, that the engineers of the various television manufacturers are now ready to devote their full attention to the further development and perfection of television.


e -m..#f-gLWWQ

44 wwm
1945 Theatre Catalog, 4th Edition, Page 596