80 BELL SYSTEM TECHNICAL JOURNAL 



out has been designed specifically to meet conditions in the United 

 States, conditions which in many respects are different in the different 

 countries. 



It is, of course, not possible in a paper of such broad scope to give 

 technical details of the engineering problems involved. These have, 

 however, been quite fully set forth in numerous articles in the tech- 

 nical press of the United States. For the convenience of those who 

 may wish to refer further to these matters, a bibliography containing 

 a selected list of some of the more impoitant articles is attached to 

 this paper. 



In looking forward, there seems to be no doubt that the develop- 

 ment of telephone communication in the United States, commercially 

 and technically, will be more rapid than in the past, not less rapid. 

 There are strong indications that in the future very much larger 

 amounts of telephone service, both exchange and toll, will be de- 

 manded than at the present time, and in fact that for a number of 

 years at least the rate of growth will continue to increase. The type 

 and extent of services supplied will be modified to meet the broaden- 

 ing and multiplying demands of the changing business and social 

 structure of the country. Finally, it is evident that the rapid advance 

 of science will continue to bring forward new possibilities by means of 

 which new and improved forms of communication systems, apparatus, 

 and materials, can be developed. 



These facts all indicate that the engineering work for the telephone 

 communication system of the United States is not complete nor de- 

 creasing in magnitude or importance, but on the contrary it is increas- 

 ing in volume and complexity and in the importance of the problems 

 to be undertaken and solved. 



Authors' Note 



The authors wish to acknowledge their indebtedness to a large 

 number of members of the organization for their assistance in the 

 preparation of this paper. It is impracticable to mention all who have 

 been of assistance but they wish to express their appreciation par- 

 ticularly to Messrs. O. B. Blackwell, W. E. Farnham, W. H. Harden, 

 H. S. Osborne, and W. A. Stevens. 



