Abstracts of Technical Articles by Bell System Authors 



Electrochemical Factors in Underground Corrosion of Lead Cable Sheath} 

 V. J. Albano. Stray current is the principle cause of corrosion failures on 

 underground telephone cables in most cities where trolleys are operated. 

 To mitigate this condition, the cable sheaths are ''drained" to the negative 

 return system of the traction system. By this means not only is the stray 

 current anodic area largely eliminated, but the cables automatically become 

 negative to earth, and therefore are cathodically protected. The cathodic 

 protection afforded in this manner prevents other types of corrosion from 

 occurring. With the gradual abandonment of trolley systems, and with the 

 extension of underground cables into non-trolley areas, the percentage of 

 underground telephone plant receiving this protection is decreasing. As a 

 result, the problems of lead corrosion due to such causes as galvanic and local 

 cell action of various types, and chemical action by substances in the soil 

 are becoming more prevalent. It is the purpose of this article to review some 

 of the basic principles of corrosion not involving stray currents, and show 

 how they apply to the problems of lead cable sheath corrosion. 



PCM Equipment,^ H. S. Black and J. O. Edson. PCM, pulse code 

 modulation, is a new solution to the problem of overcrowded frequency 

 spectrum. It appears to have exceptional possibilities from the standpoint 

 of freedom from interference, and seems to have inherent advantages over 

 other types of multiplexing. 



Coaxial-Cable Networks.^ Frank A. Cowan. This paper discusses the 

 general features of the coaxial system, its application for both telephone and 

 television, and the future prospects for very-broadband transmission facili- 

 ties in the communication network. 



Parabolic- Antenna Design for Microwaves } C. C. Cutler. This paper 

 is intended to give fundamental relations and design criteria for parabolic 

 radiators at microwave frequencies (i.e., wavelengths between 1 and 10 cen- 

 timeters). The first part of the paper discusses the properties of the para- 

 bola which make it useful as a directional antenna, and the relation of phase 

 polarization and ampUtude of primary illumination to the over-all radiation 

 characteristics. In the second part, the characteristics of practical feed 

 systems for parabolic antennas are discussed. 



1 Corrosion, October 1947. 



' Electrical Engineering, November 1947. 



' Proc. I. R. E. — Waves and Electrons Section, November 1947. 



< Proc. I. R. £., November 1947. 



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