Statistics relative to use of radio channels, prepared by Lieut. Commander T. A. M. Craven-Continued Of the 90 channels assigned to Government service, 32 are cleared channels-12 are shared with Newfoundland-3 are shared with Canada-1 must not interfere with Cuba-42 are in the mobile service, 37 of which have special protection from interference. Of the 162 channels in point to point service, 64 must not interfere with other North American nations-13 are shared with Canada and 5 are shared with Newfoundland. There are 80 cleared channels. 8 Summer only 2, 240 95 133 99 259 99 19 167 355 572 1, 798 502 to NOTE. It is estimated that, due to technical progress within the next 5 years, it will Will give an increase in telegraph channels of from. 649 639 to 1, 398 624 to 1, 400 475 to 475 2,240 to 3,922 $250,000 to $1,000,000.$50,000 to $750,000.... $3,000 to $8,000.. do. 7 5 5 do. 13 3 3 2 9 do. 18 1 6 11 18 Senator BROOKHART. Why is this called a "spectrum"? Lieutenant Commander CRAVEN. That is a difficult question to answer, sir. But these are various frequencies. They vary in the number of cycles per second. We have in light the same thing. You have light rays that always vary in frequency. And for the different colors. Senator BROOKHART. This is not a light ray in any sense, is it? Lieutenant Commander CRAVEN. It is not a light ray, but it is similar to a light ray. Senator BROOKHART. It sounds to me like putting the flag at "halfmast" when it is on a "staff”. Lieutenant Commander CRAVEN. Well, this is a little different than light. The frequencies of this are lower than the frequencies of light rays. Senator BROOKHART. My question was as to how it happened to be called a spectrum. Why should it not have some name that related to sound rather than sight? Lieutenant Commander CRAVEN. I do not know how they happened to call it "spectrum" except that the various colors translated as light values differ in values of frequencies. And the whole light band is called a spectrum. By analogy, the radio, although electrical and magnetic varies in frequencies from a lower to a higher frequency and it was called a spectrum. Just a method of comparison. Senator HOWELL. In other words, the waves are identical, except as to difference in length? Lieutenant Commander CRAVEN. Difference in length, and also one is electrical and the other is light. Senator HOWELL. Well, is not that electrical also? Lieutenant Commander CRAVEN. I am not enough of a scientist to say that. Senator BROOKHART. I think, Senator Howell, you ought to get a new scientific name for it. Lieutenant Commander CRAVEN. Then the vacuum tube, that instrument which has been responsible for the great increase of radio efficiency as we know it to-day, was not manufactured in this country to any great extent, due to an involved patent situation. In fact, the patent situation was so involved as to make it a precarious business adventure to engage in the manufacture or use of radio equipment. The companies which did engage in radio communications in the United States were, in many cases, controlled by foreign capital although incorporated under a charter issued by one of the several States of this country. Except for the Government communications, the commercial radio organizations engaged in point-to-point transoceanic communications were controlled by foreigners. Shortly after this period, of between 1912 and 1914, the World War commenced. The United States realized immediately the difficulties involved in protecting its neutrality when stations were owned or controlled by foreign interests. And we were forced to establish censorship. Then in the Government services, there was great activity in the development of radio equipment in order to be free from foreign manufacture. Commercial companies in the United States were encouraged to design and construct radio apparatus for various Government departments, especially for the Navy. The demands of |