THE BELL SYSTEM TECHNICAL JOURNAL 



Published quarterly by the 



American Telephone and Telegraph Company 



195 Broadway, New York, N. Y. 



iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 



EDITORS 

 R. W. King J. O. Perrine 



F. B. Jewett 

 A. B. Clark 

 S. Bracken 



EDITORIAL BOARD 



H. P. Charlesworth 



O. E. Buckley 



M. J. Kelly 



W. Wilson 



W. H. Harrison 

 O. B. Blackwell 

 G. Ireland 



iiimiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 



SUBSCRIPTIONS 



Subscriptions are accepted at $1.50 per year. Single copies are fifty cents each. 

 The foreign postage is 35 cents per year or 9 cents per copy. 



iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiniiii 



Copyright, 1940 

 American Telephone and Telegraph Company 



PRINTED IN U. S. A. 



