. Official proceedings . ertain amount ofspace radiation taking place as can be seen by exploring with asimple straight wire with a miniature lamp inserted in the mid-dle to indicate, by its filament lighting, when current is passing. High frequency currents of a considerable lower order offrequency, however, are being used successfully for telephoningover high tension power lines while the lines are operating nor-mally in transmitting power at very high voltages. 109 They are also used on the trunk lines of the telephone com-panys service to increase the carrying capacity of existing linesfor
. Official proceedings . ertain amount ofspace radiation taking place as can be seen by exploring with asimple straight wire with a miniature lamp inserted in the mid-dle to indicate, by its filament lighting, when current is passing. High frequency currents of a considerable lower order offrequency, however, are being used successfully for telephoningover high tension power lines while the lines are operating nor-mally in transmitting power at very high voltages. 109 They are also used on the trunk lines of the telephone com-panys service to increase the carrying capacity of existing linesfor long distance communications. Thus one pair of wires maycarry half a dozen different conversations simultaneously with-out the slightest trace of confusion. Auditorium Loud Speaker As an amplifier the vacuum tube is used in long distancetelephone service to build up the strength of the feeble voicecurrents at intervals of 40 or 50 miles. By this means con-versation from coast to coast is entirely satisfactory. The voice. C. R. Hanna, one of thre inventors, in his laboratory. The element inthe foreground is the one used in conjunction with the powerful ex-ponential horn. even though amplified many times as it passes through theseveral booster stations, is readily recognizable with all of thecharacteristics that identify one voice from another. Another use of the vacuum tube amplifier is in the talkingmovie art. Here it is necessary to build up exceedingly feeblecurrents to a strength sufficient for a loud speaker. This application promises to assume considerable import-ance in this new art now just at the beginning. 110 Still another application of the tube as an amplifier is inwhat is termed the auditorium loudspeaker. This is in effect an electrically operated phonograph. Theobject sought is improved quality of reproduction and increasedvolume. Such an apparatus is expected to be a competitor oforchestras in hotels—clubs—theaters—dance halls—parks—andin time may be
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