VOLUME XXVII APRIL, 1948 no. 2 



rmatOnn 

 THE BELL SYSTEM*"""^* 



TECHNICAL JOURNAL 



DEVOTED TO THE SCIENTIFIC AND ENGINEERING ASPECTS 

 OF ELECTRICAL COMMUNICATION 



Microwave Repeater Research H. T. Friis 183 



The Measurement of Delay Distortion in Microwave 



Repeaters D, H, Ring 247 



Frequency Shift Telegraphy — ^Radio and Wire Applications 



J. R. Davey and A. L. Matte 265 



Reflections from Circular Bends in Rectangular Wave 



Guides— Matrix Theory. S. O. Rice 305 



The Approximate Solution of Linear Differential Equations 



Marion C. Gray and S. A. Schelkunoff 350 



Potential Coefficients for Ground Return Circuits 



W. Howard Wise 365 



Abstracts of Technical Articles by Bell System Authors. . 372 



Contributors to this Issue 377 



AMERICAN TELEPHONE AND TELEGRAPH COMPANY 



NEW YORK 



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