RADIO is the combining form denoting relation to or con nection with a ray, a radius, or radiation. In anatomy the term refers to the radius or outer of the two bones of the forearm as radio-carpal. In physics and chemistry it is used in connection with various forms of radiation as in radio-activity (q.v.). In elec tricity its general application is in association with electric waves (q.v.). In its specific application to radio communication the word is used to denote the transmission and reception of signals by means of radiated electromagnetic waves. The signals translated may be the ordinary sounds sensed by the ear or they may be the "signals" of images sensed by the eye which have been trans lated into "sound" signals, as in television. Communication by radio in its various forms, including such phases as wired wireless, wireless telegraphy, wireless telephone, general types of broad casting, television, is too broad a subject to be treated adequately in a single article.
A basic discussion of atmospheric electricity is given in the article ELECTRICITY, ATMOSPHERIC. A study of the theory of Maxwell and others in the development of theory relative to elec tric waves is found in the article ELECTRIC WAVES. The theoreti cal concepts of wireless telegraphy are in the article WIRELESS TELEGRAPHY; the practical applications, including such data as international agreements, standard wave lengths, maps of com munication lines throughout the world, are in the same article under a subheading, Communication by Wireless.
The principles of the action of heat on matter in generating atomic or subatomic electrically charged particles are found in the article THERMIONICS, while the article THERMIONIC VALVES treats of the several distinct types of vacuum tubes. The more important and most frequently encountered radio terms, number ing several score, are defined and described under their respective headings. The short radio subjects are in turn cross-referred to in the main practical articles listed below.
Television is found under the heading TELEVISION and the transmission of motion pictures by this and other means is dis cussed under the articles TELEVISION and MOTION PICTURE: Technology. Under TELEGRAPH and TELEPHONE iS a study of
transoceanic wireless telephone and wired wireless. All articles are supplemented by text illustration and photographs and, in many instances, by diagrams showing wiring arrangements and important technical data.
For the convenience of the reader the subject of broadcasting is divided into two main headings: (I) BROADCASTING and (2) BROADCAST MUSIC. The former article is subdivided into (a) a general survey of European practice, (b) a general survey of American practice, (c) tecnnical aspects or the engineering prob lems involved in broadcasting. The latter article is subdivided into two sections : (a) broadcast music in Great Britain and on the Continent and (b) broadcast music in America. In addition, the two major phases of broadcasting—reception and transmission- are dealt with in RADIO RECEIVER and MICROPHONE OR TELE PHONE TRANSMITTER.
So many new developments are occurring in radio that it is impossible for a survey to predict tendencies even a few years hence; it is believed helpful, however, to include here the most important "peaks" that have been made in wireless progress. The following data are taken from an official bulletin of the U.S. Department of Commerce: In 1827 Savary found that a steel needle could be magnetized by the discharge from a Leyden jar. In 1837 the first patent for an electric telegraph was taken out by Cooke and Wheatstone (London) and by Morse (United States). In 1840 Henry first produced high-frequency electric oscillations. In 1867 Maxwell read a paper from the Royal Society in which he laid down the theory of electromagnetism, which he developed more fully in 1873 in his electric waves that are now used in wireless teleg raphy. In 1870 Von Bezold discovered that oscillations set up by a condenser discharge in a conductor give rise to interference phenomena.