Kiebitz, Zeitschr. f. H. F. Tec., p. 141 ; Wireless Age, p. 55 (1923) ; White Paper 143 (3oth July, 1924) ; Pession & Pizzuti, L'Ettro tecnica, 12, 171 (1925) ; Heising, Schelleng & Southworth, Proc. Inst. Radio Eng., 14, 613 (1926) ; B. van der Pol, De Ingenieur, 46 ; T. L. Eckersley, Jour. Inst. El. Eng., 65, 600 (1927) ; Oswald & Deloraine, Electrician, 96, 572 (1926) ; E. H. Shaughnessy, Jour. Inst. El. Eng., 64, 683 (1926) ; The Engineer, 141, 78 (1928) ; Hallborg, Briggs & Hansell, Proc. Inst. Radio Eng., 15, 467 (19z7). (W. E.) Aviation and Wireless.—The possibilities of radio as an aid to flight are being actively developed along the following lines: (I) communication, (2) course navigation, (3) field local izing and (4) general. This last includes miscellaneous develop
ments such as radio altimeter devices. See RADIO; AERONAUTICAL ARTICLES. The radio directive beacon system is a special kind of radio station usually situated just off the landing field. In stead of having the single antenna, as in the ordinary station, it has two loop antennae at an angle with each other. Each emits a set of waves which is directive, i.e., stronger in one direction than another. When an aeroplane flies along the line exactly equi distant from the two beams of radio waves it receives a signal of equal intensity from the two. If the aeroplane gets off this line it receives a stronger signal from one than the other. The indicator on the instrument board shows when the signals from the two beams are received with equal intensity by means of two small vibrating reeds. The tips of the reeds are white in a dark back ground, so that when vibrating upon receiving signals they appear in a vertical straight line. The reed on the pilot's right is turned to a frequency of 65 cycles and the one on the left to 85 cycles. This system is to be installed on all American air routes. (X.)