THE BELL SYSTEM TECHNICAL JOURNAL 



PUBLISHED QUARTERLY BY THE 



AMERICAN TELEPHONE AND TELEGRAPH COMPANY 



195 BROADWAY, NEW YORK 7, N. Y. 



CLEO F. CRAIG, President 



CARROLL O. BICKELHAUPT, Secretary 



DONALD R. BELCHER, Treasurer 



EDITORIAL BOARD 



F. R. KAPPEL O. E. BUCKLEY 



H.S.OSBORNE M.J.KELLY 



J. J. PILLIOD A.B.CLARK 



R. BOWN D. A. QUARLES 

 F. J. FE E LY 



P. C. JONES, Editor 

 M. E. STRIEBY, Managing Editor 



S U H S C R I r T I O N S 



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



PRINTED IN U.S.A. 



