^VOLUME XIX OCTOBER, 1940 number 4 



THE BELL SYSTEM 



TECHNICAL JOURNAL 



DEVOTED TO THE SCIENTIHC AND ENGINEERING ASPECTS 

 OF ELECTRICAL COMMUNICATION 



The Carrier Nature of Speech — Homer Dudley 495 



Manufacture of Quartz Crystal Filters — G. K. Burns . . .516 



Results of the World's Fair Hearing Tests 



— J. C. Steinberg, H. C. Montgomery, and M. B. Gardner 533 



The Subjective Sharpness of Simulated Television Images 



^Millard W. Baldwin, Jr, 563 



Cross-Modulation Requirements on Multichannel Amplifiers 



Below Overload— PT. R. Bennett 587 



Radio Extension Links to the Telephone System 



— R. A, Heising 611 



Abstracts of Technical Papers 647 



Contributors to this Issue 651 



AMERICAN TELEPHONE AND TELEGRAPH COMPANY 



NEW YORK 



50c per Copy $1,50 per Year 



