594 BELL SYSTEM TECHNICAL JOURNAL 



8,000-cycle low-pass filter was included under both conditions it was 

 found that listeners had considerable difficulty in consistently picking 

 a difference. In fact, the ordinary observer could not be relied upon 

 to pick differences consistently even when the 8,000-cycle filter was 

 not included. 



Conclusion 



This development was undertaken to provide a system for obtaining 

 satisfactory channels for the transmission of broadcast programs in 

 the rapidly growing cable network of the Bell Telephone System. 

 The time required to complete such a development and the need for 

 advance planning in the cable plant made it essential that the channels 

 be adequate to render service for a number of years. Improvements 

 in broadcast reproduction may be expected to continue and may 

 very well result in changes in the present frequency allocations to 

 give space for wider bands. The cable system described in this paper 

 was, therefore, developed to possess transmission characteristics supe- 

 rior to present-day radio systems, the margin anticipating improve- 

 ments which may take place in the future. 



Acknowledgment 



The authors gratefully acknowledge the assistance of many of their 

 associates in the preparation of this paper and particularly of Mr. H. 

 S. Hamilton. 



