VOLUME XIV JANUARY, i93'5:;' ■■::.,';:.' 



..... ■ . . ' ' ^-j f ■ ' ' • . ' 



iSilMBER 1 



THE BELL SYSTEM 



TECHMCAL JOURNAL 



DEVOTED TO THE SCIENTIFIC AND ENGINEERING ASPECTS 

 OF ELECTRICAL COMMUNICATION 



Wide Band Transmission Over Balanced Circuits — 



A. B Clark 1 



A Survey of Magnetic Materials in Relation to 



Structure— T^. C. Ellis and Earle E. Schumacher 8 



Theory of Multi-Electrode Vacuum Tubes — 



H. A. Pidgeon 44 



Limits to Amplification — 



J. B. Johnson and F. B. Llewellyn 85 



Vacuum Tubes as High-Frequency Oscillators — 



M. J. Kelly and A. L. Samuel 97 



Horizontal Rhombic Antennas — 



E. Bruce, A. C. Beck and L. R. Lowry 135 



Extraneous Frequencies Generated in Air Carrying 

 Intense Sound Waves — 



A. L. Thuras, R. T. Jenkins and H. T. O'Neil 159 



Abstracts of Technical Papers 173 



Contributors to this Issue 176 



AMERICAN TELEPHONE AND TELEGRAPH COMPANY 



NEW YORK 



50c per Copy $1,50 per Year 



