WORLD-WIDE TELEPHONY 493 



the part time use of a circuit, the apparatus being arranged to share 

 its time between two or more distant terminals. 



One cannot help being impressed by the developments represented 

 by Fig. 3, which have taken place in the short space of five years. 

 We are, nevertheless, in an early stage of development and present 

 service suffers from the limitations of pioneer conditions. Dependence 

 in so many cases upon a single intercontinental circuit which often is 

 shared on a "party line" basis between two or more terminal points, 

 is one of these limitations. Another is the variation in transmission 

 characteristics and the susceptibility to interruptions which in the 

 present stage of development of radio are characteristic especially of 

 short-wave circuits on some of the more important routes. The 

 rapidity with which the first steps have been taken is perhaps the 

 best assurance that advance will continue to be rapid as the commercial 

 demand for increasing amounts of service develops. This is illustrated 

 by Figs. 4 and 5 which show the intercontinental circuits of the 

 world which will exist when the present plans for additional circuits 

 have been completed in so far as these plans are known to the authors. 



Fig. 6 shows the extent to which the countries of the world will be 

 tied into one great telephone system when the plans outlined in 

 Figs. 4 and 5 are completed. Fig. 6 also shows the distribution of 

 world trade and population of various groups of countries which are 

 so interconnected. It will be noticed that the world-wide telephone 

 network will include countries having 99 per cent of all the telephones 

 of the world and having 92 per cent of the world's foreign trade. 

 Details of all the present and proposed circuits which have come to the 

 knowledge of the authors are given in Appendix I. 



Closely related to the establishment of intercontinental circuits is 

 the establishment of telephone service from European and North 

 American points to a number of passenger vessels normally operating 

 on the North Atlantic and other passenger routes. In addition, 

 work is advancing in the equipment of fishing fleets, tugs, etc., but 

 this service pertains more directly to the continental telephone service. 



Technical Problems and Limitations 

 The unusual technical difficulties of providing satisfactory inter- 

 continental telephone circuits come about not merely because of the 

 distances involved but because these distances include long stretches 

 of sea or undeveloped land. For years prior to the establishment of 

 the first intercontinental circuit, commercial service was given on 

 continental telephone networks over comparable distances, for ex- 

 ample, in North America up to about 6000 miles (10,000 kilometers). 



