536 MAGNETISM AND ELECTRICITY frequency-modulation system, the broadcasting station and the receiver are tuned to waves of a certain amplitude so that other waves of the same frequency will not produce any interference unless they are of the same amplitude. Frequency modulation employs ultrashort radio waves, and therefore broadcasting beyond the horizon is not possible because the ultrashort radio waves are not reflected back to the earth by the ionized layer of gases known as the Heaviside layer in the upper atmosphere as are the longer radio waves. This limitation of frequency-modulation broadcasting would really be an advantage because there would not be any interference from distant stations. The range of frequencymodulation broadcasting stations is constant both day and night. If two stations using frequency modulation were broadcasting on the same frequency, only the more powerful station would be heard. Frequency modulation makes possible many more broadcasting stations and makes operation costs of a station much lower because less power is required. Facsimile Broadcasting Has Many Possibilities for Important Applications in Modem Life. Tabloid newspapers are already being broadcast by a number of radio stations. These newspapers are received and printed by instruments similar to those that transmit photographs by wireless. They are capable of printing five 83^^ X 11 pages an hour. Plans were under way in 1940 to print newspapers on ocean liners by facsimile from shore transmitters. Facsimile broadcasting is four times as fast as teletype. It is now being installed in police cars to transmit photographs of wanted criminals, fingerprints, and messages which are thus available in a permanent form. One might well imagine a vast system of facsimile broadcasting that would take the place of our mail system for many short communications where time is important, thus filling the gap between telegraph and mail facilities. The Radio Has Revolutionized Communication. The dramatic evolution of the radio within one decade from a mysterious plaything to the almost universally accepted instrument of entertainment and mass communication has few counterparts in social history. Commercial broadcasting was begun only in 1920, and yet twelve years later it was estimated that over sixteen million receiving sets were in use. The radio and the other agencies of com-
RADIO GENERATION AND RECEPTION 537 munication, such as the telephone, the telegraph, and rapid mail systems, have brought extreme complexity to modern society, but at the same time they have made for greater homogeneity. The radio, perhaps more than any other development of recent years, has helped to curtail the trend away from the home. The radio, television, and the sound motion picture present an opportunity for powerful interests, private or public, to indoctrinate the people with prepared opinions. Fig. 264. Radio facsimile receiver. Courtesy of the R.C.A. Manufacturing Company, Inc.) The management of communications may well be the most critical factor in maintaining liberty. One of the great problems facing American democracy is that of so managing its communications that free discussion and criticism and unbiased and unlimited dissemination of knowledge may be maintained. Government control should not be of the type found in totalitarian states, where the government determines what is to be spoken or printed. Government control of communications in a democracy should exist only to maintain the freedom of communications and to prevent them from being used for dishonest and debasing purposes.