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BELL SYSTEM TECHNICAL JOURNAL 



taken on the United States-Europe route and which show, for com- 

 parison, the relatively stable conditions for the long- wave channel. 

 In many respects short-wave and long-wave radio channels admirably 

 supplement each other, being seldom interrupted at the same time. 



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GREENWICH MEAN TIME 



Fig. 8 — Diurnal field strength characteristics of long and short-wave transmission 

 over the North Atlantic. Shows effect of sunrise and sunset on the long wave and 

 the necessity with short waves for using different wave-lengths at different times 

 of day. 



Short-wave transmission is in an early stage of development and it 

 may be hoped that, with further experience, means will be found to 

 avoid or reduce at least some of the present major limitations. 



Wire Circuits 



The intercontinental routes offer great difficulties to the placing 

 of wire circuits. However, the limitations of radio, particularly on 

 the intercontinental routes between North America and Europe 

 interconnecting the two largest continental groups of telephones, have 

 naturally led to considerable engineering thought on the possibilities 

 of wire circuits. The most interesting development in this connection 

 is a submarine cable which can be used for long lengths without 

 intermediate repeaters. 



