142 BELL SYSTEM TECHNICAL JOURNAL 



Part I 



RADIO SYSTEM-DESIGN AND ESTABLISHMENT 

 OF STATIONS 



General Plans 



The fundamental condition laid down at the beginning of this 

 work was the very general one that there should be developed a system 

 by which any telephone subscriber of the Bell System could carry on 

 a conversation with a telephone station located on a ship, and that, 

 from the point of view of the speakers, the operation should be similar 

 to the carrying on of an ordinary toll call between land wire subscribers. 

 This, of course, involves the development of a satisfactory two-way 

 radio telephone system for ship use. Furthermore, it was desired 

 to be able to carry on three simultaneous and independent conversa- 

 tions between three ships and one land station, since a final commercial 

 system will involve the establishment of several circuits simultane- 

 ously. These 2-way transmissions were to be obtained without em- 

 ploying an excessively large frequency band. 



A rough study of the problem resulted in a decision to locate the 

 experimental land stations about 200 or 250 miles (320 or 400 km.) 

 apart and to try for reliable commercial transmission to ships at a 

 distance of approximately 200 miles (320 km.). 



The transmission problems involved in this work, which were 

 different from those in wire telephone engineering, were: 



(a) A much greater variability in the transmission equivalent to 

 be expected in the radio link; 



(b) A much greater and more variable interference, both natural 

 and artificial; 



(c) A lack of secrecy in the sense of a wire system ; 



(d) Greater possibilities of cross-talk between channels because of 

 the use of a single medium; 



(e) More complication in the matter of signaling and in the setting 

 up of the telephone circuit. 



The apparatus problems were, of course, entirely different from 

 those of wire transmission and will not be considered in detail in this 

 paper. 



An engineering project of this kind divides itself naturally into 

 two phases; that of the development in the laboratory of systems 

 and apparatus which are technically suitable for the work and, second, 

 the providing in the field of a model system, incorporating the knowl- 



