VOLUME XXX JANUARY 1951 no. i 



THE BELL SYSTEM 



TECHNICAL JOURNAL 



DEVOTED TO THE SCIENTIFIC AND ENGINEERING ASPECTS 

 OF ELECTRICAL COMMUNICATION 





The Type N-1 Carrier Telephone System: Objectives and 

 Transmission Features R. S. Caruthers 1 



Television by Pulse Code Modulation W. M. Goodall 33 



Prediction and Entropy of Printed EngUsh . C. E. Shannon 50 



A Submarine Telephone Cable with Submerged Repeaters 



/. J. Gilbert 65 



Theory of the Negative Impedance Converter 



J. L, Merrill 88 



The Ring Armature Telephone Receiver 



E. E. Mott and R. C. Miner 110 



Internal Temperatures of Relay Windings R. L. Peek 141 



The Evolution of Inductive Loading for Bell System Tele- 

 phone Facilities T. Shaio 149 



Technical Publications by Bell System Authors Other Than 

 in The Bell System Technical Journal 205 



Contributors to this Issue 211 



30^ Copyright, 1951 $1.30 



per copy American Telephone and Telegraph Company p^^ Year 



