NOTES in 



The Present Position of Wireless Telephony (Philip R. Coursey, B.Sc. 

 (Eng.), A.M.I.E.E.) 



One of the greatest obstacles in the way of successful wireless speech transmission, 

 as distinct from mere telegraphic signalling, has been that of modulating the 

 high-frequency power output of the transmitting station in accordance with the 

 speech form, and of accomplishing this modulation by means of the minute energy 

 associated with ordinary sound-waves in air. 



The employment of the three-electrode valve — first invented in its earlier two- 

 electrode form by Dr. J. A. Fleming, and subsequently developed by many 

 workers — has greatly simplified the modulation problem. It has also at the same 

 time provided a simple and extremely reliable form of high frequency continuous 

 oscillation generator, suitable at present for moderate power work. 



Under the stimulating influence of war-time requirements, the developments 

 in the design and construction of these valves have progressed rapidly, so that 

 their manufacture in quantity is now no very difficult matter. The first serious 

 attempts at radiotelephony with the use of valves were made about 191 4, and 

 developments in America in that and the following year led, in October 191 5, 

 to the successful wireless transmission of human speech over a range of 5,000 

 miles from Arlington (U.S.A.) to Honolulu. The Atlantic was also bridged 

 between Arlington and the Eiffel Tower at the same time. These tests were 

 essentially of an experimental nature to test the possibilities of the valve for 

 such purposes. 



This, then, was the position of long-distance radiotelephony at the close 

 of 191 5. During the war no specially important attempts have been made relative 

 to the use of wireless telephony over great distances, since the naval and military 

 requirements have been of an essentially different nature. In general only very 

 short-range work has been required. For these purposes the small valve trans- 

 mitters have proved of very great value. 



Wireless telephone sets have been developed for ship-to-ship work between 

 the various units of a squadron, to secure rapid co-ordination of action and 

 centralisation of control. The apparatus has also been used by the American 

 Navy to enable the ship's captains to report direct to the Base Headquarters 

 on shore, but of necessity the bulk of such traffic has been in the form of coded 

 telegraphic messages. Undoubtedly the most spectacular application has been 

 to aircraft, and for the control of such craft direct from the ground. The 

 commanding officer on the ground can now issue his spoken orders direct to the 

 pilots of the squadron some miles away, thus immensely simplifying the planning 

 and carrying out of aerial operations. 



The application of radiotelephony to aircraft is likely to be an increasingly 

 important feature of peace-time flying, especially for maintaining touch with land 

 during long-distance flights, and in conjunction with direction-finding apparatus 

 to aid navigation. The tendency of recent developments of the telephone 

 apparatus has been in the direction of reducing the power of the transmitter, 

 and increasing the range by using more sensitive receivers with valve amplifiers. 

 A recent achievement on these lines has been the respanning of the Atlantic 

 by the spoken word from Ireland to Canada, by the Marconi Company, the object 

 being to investigate the feasibility of commercial working. 



The other important applications of radiotelephony must not, however, be lost 

 sight of in the natural interest in new developments. As examples we may 

 mention its uses for ordinary ship-to-ship, and ship-to-shore business traffic, for 



