Abstracts of Technical Articles by Bell System Authors 



Testing Cathode Materials in Factory Production} J. T. Acker. The paper 

 deals with the methods of testing radio-tube cathode materials in factory 

 production, and especially with a comparison of several specific lots of 

 materials of variable content. It is believed that this is the first time the 

 electron-tube industry has made mass tests on a well-controlled engineering 

 basis of cathode materials which vary in single component elements. 



Advances in the Theory of Ferromagnetism? R. M. Bozorth. This article 

 presents the results of the most recent investigations in the field of ferro- 

 magnetism. There have been a number of new ideas brought forth through 

 research along these lines, of which three of the most outstanding ones are 

 explained and illustrated. 



On Magnetic Remanence.^ R. M. Bozorth. The magnetic retentivity of 

 many materials is about half of the magnetization at saturation, a fact ac- 

 counted for by simple domain theory. In some materials, however, the re- 

 tentivity is only a small fraction of saturation, sometimes less than 10 per 

 cent. The explanation of this fact is discussed. It is suggested that in mate- 

 rials with almost zero magnetic anisotropy the Bloch walls between domains 

 increase in thickness until they envelop the whole specimen and the domain 

 structure disappears. 



Multijrequency Pulsing in Sivitching} C. A. Dahlbom, A. W. Horton, 

 Jr., and D. L. Moody. Applications of multifrequency pulsing in switching 

 are described in this article. Today, many installations of this type are 

 being made in cities throughout the nation. This system permits operators 

 or senders to complete calls to crossbar offices without the aid of other 

 operators. 



Circuits for Cold Cathode Gloiv Tubes} W. A. Depp and W. H. T. Holden. 

 This paper discusses fundamental operating characteristics and typical cir- 

 cuits using cold cathode glow tubes for relays, impulse generators, pulse 

 counting and interlocking functions. 



The Substitution Method of Measuring the Open Circuit Voltage Generated 

 by a Microphone.^ M. S. H.wvley. An analysis of the substitution method 

 of measuring the open circuit voltage generated by a microi)hone is given 



1 Proc. I.R.E.—Waves and Electrons Section, v. 37, pp. 688-690, June 1949. 



2£/ec. Engg., v. 68, pp. 471-476, June 1949. 



^Zeils.f. Physiti, v. 124, 7/12, pp. 519-527, 1948. 



^ Elec. Engg., v. 68, pp. 505-510, June 1949. 



6 Elec. Mfg., V. 44, pp. 92-97, July 1949. 



^Jour. Acous. Soc. Amer., v. 21, pp. 183-189, ^Slay 1949. 



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