Audion

Collier's New Encyclopedia (1921)

a vacuum-tube device invented by Dr. L. de Forest and employed extensively in recent wireless telegraphy and telephony, as well as in long-distance wire telephony. It consists of a tube or bulb containing a heated metal filament, a metal plate at some distance from the filament, and a wire grid between the two. As was found by Fleming in 1905, an electric current will flow in but one direction between plate and filament, thus making it pos possible, by using the tube, to convert the alternating current set up by incoming radio waves into the unidirectional current necessary for the reproduction of sounds in telephone receivers. The grid of the audion is connected with the antennæ of the wireless station. Any waves received and communicated to it affect the intensity of a small current in the tube kept constantly flowing from the plate to the filament, and these variations in the so-called plate circuit are communicated to the telephone receivers connected into that circuit, where they produce sounds similar to the ones which set up the original radio waves. The audion is used not only as a detector, but may be employed as an amplifier of signals. Amplifications of over a million times the original signals have already been produced by cumulative arrangements, and the feeling of radio engineers is that, great as have been the accomplishments of the vacuum tube in the recent past, they will prove to be insignificant in comparison with its accomplishments of the future. The audion was first used for detection purposes only, but it has recently been developed in larger forms for the generation of radio waves as well, and this use is rapidly increasing. The above-described process is here practically reversed, variations in made to produce the plate circuit being oscillations in the so-called grid, by which in turn they are communicated to the aerial circuit. The advantages of the vacuum-tube transmitter lie in the greater range attainable by the continuous waves generated, the lower voltages required in operation, and the consequently lowered dangers and costs. Generating audions were called oscillions by De Forest. Recent types called pleiotrons are developing great possibilities. (See WIRELESS TELEPHONY.) AUSTRIA. First president of republic elected Dec. 9, 1920 (Dr. Michael Hainisch, Pan-German Christian Socialist candidate). Desperate economic conditions led to note to the powers (Jan. 11, 1921) that the Austrian Government was willing to retire and put administration into hands of Reparation Commission. Peace treaty with Ū. S. Ratifications exchanged Nov. 8, 1921. Treaty of commerce with Soviet Russia (Dec. 8, 1921). American dollar quoted in Vienna at 10,- 000 kronen (January, 1922). Area, 30,- 716 square miles. Population (1920), 6,139,197.