494 



BELL SYSTEM TECHNICAL JOURNAL 



World Distribution 

 Population, Telephones, Foreign Trade 



For Countries Having Existing or Proposed International Telephone Connections as oj 



January 1, 1932 



Fig. 6. 



The technique of transmission over long continental distances, how- 

 ever, includes as one fundamental element the use of intermediate 

 amplification at frequent intervals of from 45 to 240 miles (75 to 400 

 kilometers) , depending upon the electrical characteristics of the circuit. 



