

THE BELL SYSTEM 



TECHNICAL JOURNAL 



A JOURNAL DEVOTED TO THE 



SCIENTIFIC AND ENGINEERING 



ASPECTS OF ELECTRICAL 



COMMUNICATION 



EDITORIAL BOARD 



Bancroft Gherardi F. B. Jewett 



H. P. Charlesworth W. H. Harrison E. H. Colpitts 



L. F. Morehouse H. D. Arnold O. B. Blackwell 



Philander Norton, Editor J. O. Perrine, Associate Editor 



INDEX 



VOLUME IX 



1930 



AMERICAN TELEPHONE AND TELEGRAPH COMPANY 



NEW YORK 



