THE BELL SYSTEM TECHNICAL JOURNAL 



Published quarterly by the 



American Telephone and Telegraph Company 



195 Broadway, New York, N. Y. 



EDITORS 



R. W. King J. O. Perrine 



EDITORLA.L BOARD 



C. F. Craig O. E. Buckley 



O. B. BlackweU M. J. KeUy 



H. S. Osborne A. B. Clark 



J. J. PiUiod F. J. Feely 



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SUBSCRIPTIONS 



Subscriptions are accepted at $1.50 per year. Single copies are 50 cents each. 

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



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Copyright, 1949 

 American Telephone and Telegraph Company 



PRINTED IN UiS.Ai 



