THE BELL SYSTEM 



TECHNICAL JOURNAL 



VOLUME X, 1931 

 Table of Contents 



January, 1931 



The Detection of Two Modulated Waves which Differ SHghtly in 



Carrier Frequency — Charles B. Aiken 1 



A Magnetic Curve Tracer — F. E. Haivortli 20 



A Multi-Channel Television Apparatus — Herbert E. Ives 33 



Condenser and Carbon Microphones — Their Construction and Use 



—W. C. Jones 46 

 Certain Factors Affecting the Gain of Directive Antennas — 



G. C. Soiithworth 63 

 Absolute Calibration of Condenser Transmitters — L. J. S'wian ... 96 

 Rating the Transmission Performance of Telephone Circuits — 



W. H. Martin 116 

 Paragutta, A New Insulating Material for Submarine Cables — 



A. R. Kemp 132 



April, 1931 



Symposium on Coordination of Power and Telephone Plant 



Introductory Remarks — R. F. Pack 155 



I — Trends in Telephone and Power Practise as Affecting 



Coordination — IV. H. Harrison and A. E. Silver ... 159 

 II — Status of Joint Development and Research on Noise Fre- 

 quency Induction — H. L. Wills and 0. B. Blackivell 184 

 III — Status of Joint Development and Research on Low-Fre- 

 quency Induction — R. N. Comvell and H. S. Warren 206 

 IV — Status of Cooperative Work on Joint Use of Poles — 



/. C. Martin and H. L. Hither 231 



Closing Remarks — B. Gherardi 241 



Overseas Radio Extensions to Wire Telephone Networks — 



Lloyd Espenschied and William Wilson 243 

 Some Optical Features in Two-Way Television — Herbert E. Ives 265 

 Bayes' Theorem : An Expository Presentation — Edimrd C. Molina 273 

 Extensions to the Theory and Design of Electric Wave-Filters — 



Otto J. Zobel 284 



