244 BKLL SYSTEM TECHNICAL JOURNAL 



of tliein into a world-wide telephone network appeal to the imagi- 

 nation and challenge the best efforts of communication engineers. 

 Especially is this development of interest to radio engineers since in 

 this pioneering stage the interconnecting links are being forged by 

 radio. W'ork is also going forward in the development of new types 

 of submarine telephone cables for this purpose and undoubtedly such 

 cables will in time play a large part in fortifying the more important 

 of the world routes. The radio part of the picture is, however, quite 

 enough in itself and this paper is, therefore, largely confined to this 

 phase of the subject. 



There is given first, a sketch of the wire telephone networks and the 

 interconnecting links as they exist today, second, a picture of the 

 transmission results which are being obtained in the operation of 

 some of these overseas links, and finally, a discussion of the more 

 important phenomena and problems involved in the radio trans- 

 mitting medium. 



The Existing World Telephone Picture 



A simplified picture of the present telephone development of the 

 world is given in the map of Fig. 1. Only the principal areas of tele- 

 phone development are indicated, by the shaded portion, and only the 

 more important routes of the wire networks have been sketched in. 

 The figures give the approximate number of telephone subscribers in 

 each continental area. 



It is, of course, these networks which give direct access to millions 

 of people in offtces and homes and permit of the personal contact 

 which characterizes telephone communication. It is natural, there- 

 fore, that they should be the foundation of the world-wide system 

 which is growing up. The larger of these networks already spread 

 over national boundaries so that the engineering problem is primarily 

 one of interconnecting the networks, generally comprising groups of 

 countries, rather than that of directly interconnecting by radio all of 

 the component countries. The points within each network at which 

 the interconnections are made may be expected to be determined 

 largely by considerations of traffic and of operating efficiency. The 

 differences of time and of languages between these w^idely separated 

 areas, and, of course, the expense of providing reliable interconnec- 

 tions over these distances, are factors which will naturally limit the 

 volume of use to be made of these connections. That they are des- 

 tined to fulfill a very real need is already proven, however, by the 

 services which are now being given. 



