160 BELL SYSTEM TECHNICAL JOURNAL 



The book will be welcomed particularly by those who at one time or 

 another have had a general acquaintance with radio-activity, cosmic rays 

 and the results of cloud chamber research, but whose vocational activities 

 have forced such special knowledge well into the nebulous regions of their 

 memories. 



Xehcork Theory Comes of Age. ^ R. L. Dietzold. The third decade in 

 the growth of modern network theory, the decade of maturity, is considered 

 in this review of the advances in network theory evolved over the past ten 

 years. New types of networks developed during the war are included. 



Thermistors as Components Open Product Design Horizons^ K. P. 

 DowELL. These thermally sensitive resistors with high negative tempera- 

 ture coefficients have come a long way since they were laboratory curiosities 

 and are now available in a wide range of types with diverse and stable char- 

 acteristics. You may be able to transfer to your own problems some of the 

 unusual design ideas described here. 



Gas Pressure for Telephone Cables}^ R. C. Giese. Communication 

 cables consist of a number of electric conductors insulated from one another 

 and encased in a metal sheath. This encasement is subjected to numerous 

 hazards, such as those caused by electrolysis, crystallization, various kinds 

 of mechanical damage, and lightning burns. Any damage to the sheath 

 which will permit water to enter the cable will decrease the effectiveness of 

 the insulation material and thus cause an impairment or an interruption to 

 the service. The entrance of moisture through small openings in the sheath 

 can be materially retarded when the space inside the cable, not occupied by 

 the conductors or insulation, is filled with a gas maintained under controlled 

 conditions. Nitrogen is the gas usually used for this purpose because it 

 is inert and does not combine chemically with the conductors or insulation. 

 In addition the use of the gas provides a method of locating openings in the 

 sheath by means of a pressure gradient, which is a material aid in cable main- 

 tenance. 



Rural Radiotelephone Experiment at Cheyenne Wells, Colo}'^ J. Harold 

 Moore, Paul K. Seyler and S. B. Wright. The first rural party-line 

 telephone service by radio installations operating on the subscribers' prem- 

 ises was inaugurated August 20, 1946. This paper describes the equipment 

 used, how it operates, and the results obtained during the preliminary testing 

 and the initial period of regular operation. Radio is one of several new 

 methods which the Bell System is exploring in its program for extension of 

 telephone service in rural areas. It is expected that experience gained in 



8 Electrical Engineering, September 1948 (pp. 895-899). 

 ' Elec'l. Mfg., August 1948 (pp. 84-91). 

 10 Transactions, A. I. E. E., vol. 66, 1947 (pp. 471-478). 

 '1 Trans. A. I.E. E., vol. 66, 1947 (pp. 525-528). 



