Abstract :
In the light of the theory of the communication of ¿information,¿ this paper reviews both the nature of television signals and a number of devices which have been proposed to improve the ratio of picture-quality to bandwidth. Part 1 examines the characteristics of the spectrum of the signals generated by the conventional method of scanning a picture, and draws attention to some little-known theoretical limitations. Part 2 describes two proposals for reducing shared-channel interference. Part 3 reviews, in relation to ¿communication theory¿ and to the form of spectrum found in Part 1, a number of devices which have been proposed either for reducing bandwidth or for transmitting additional information through the existing bandwidth.
