VOLUME XXVII JULY, 1948 no. 3 



UmmSSm 



THE BELL SYSTEM * 



TECHNICAL JOURNAL 



DEVOTED TO THE SCIENTIFIC AND ENGINEERING ASPECTS 

 OF ELECTRICAL COMMUNICATION 



A Mathematical Theory of Communication . .C,E, Shannon 379 



An Aspect of the Dialing Behavior of Subscribers and Its 

 Effect on the Trunk Plant Charles Clos 424 



Spectra of Quantized Signals W,R. Bennett 446 



Analysis and Performance of Waveguide -Hybrid Rings 

 for Microwaves H,T, Budenbom 473 



Methods of Electromagnetic Field Analysis 



S.A.Schelkunoff 487 



The Evolution of the Quartz Crystal Clock 



Warren A, Marrison 510 



Abstracts of Technical Articles by Bell System Authors . . 589 



Contributors to this Issue 591 



AMERICAN TELEPHONE AND TELEGRAPH COMPANY 



NEW YORK 



50i per copy $h50 per Year 



