TO HEAR AEROPLANES

Radio Record, Volume I, Issue 19, 25 November 1927, Page 4

TO HEAR AEROPLANES

NEW RADIO DIEVICH. If future wars are to be fought in the air, as some military authorities contend, a new radio amplifying device, developed by the U.S. Bureau of Standards, should become the most yaluable equipment in the defence of large cities. It consists of a large horn, 2 perlerated brass plate, an aluminium diaphragm, and a radio amplifier, a combination that makes it possible to detect the sound of au acroplane 20 miles away More surprising than this is its ability to differentiate the whirriug neise of an aeroplane from any other sounds, Furthermore, it tells the direction of the sound over distances of from cight to ten miles, During the Great War the French had amplifying devices in Paris to give warning of the approach of enemy aeroplanes, but these were of rather a primitive character as compared with the latest American device,