

THE BELL SYSTEM 



TECHNICAL JOURNAL 



A JOURNAL DEVOTED TO THE 



SCIENTIFIC AND ENGINEERING 



ASPECTS OF ELECTRICAL 



COMMUNICATION 



EDITORIAL BOARD 



F. B. Jewett H. p. Charlesworth W. H. Harrison 



A. F. Dixon O. E. Buckley O. B. Blackwell 



S. Bracken M. J. Kelly G. Ireland 



W. Wilson 

 R. W. King, Editor J. O. Perrine, Associate Editor 



TABLE OF CONTENTS 



AND 



INDEX 



VOLUME XVIII 

 1939 



AMERICAN TELEPHONE AND TELEGRAPH COMPANY 



NEW YORK 



