210 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1952 



Under the name ferroelectrics are classified those materials which exhibit 

 dielectric anomahes phenomenologically similar to the magnetic l^eliavior of 

 the ferromagnetics. Perhaps it would have been more logical to use the term 

 Rochelle-electrics, thus emphasizing the similarity in the dielectric behavior to 

 that of Rochelle salt. 



In this paper the known ferroelectrics are listed first, and then there follows 

 a discussion of the various theories which have been created to explain them. 



Data on Random-Noise Requirements jar Theater Television * P. 

 Mertzi. Jl. S.M.P.T.E., 57, pp. 89-107, Aug., 1951. 



Provisional evaluation of permissible random noise for theater television is 

 considered from several sources of information. These cover broadcast television 

 experience and the graininess in motion picture film; the recjuirements deduced 

 from the various sources generally agree. For broadcast television, a frequency 

 weighting and hmit on weighted noise power have been used. The finer picture 

 detail of theater television presumes a lower permissible random noise. Changes 

 in weighting curve are discussed. A hmit figure of noise is suggested, which is 

 comparable to graininess effects in motion pictures, though slightly more severe 

 than present published performance on camera tubes. 



A Spatial Harinonic Traveling-Wave Amplifier for Six Millimeters 

 Wavelength.* S. Millman^ Proc. I.R.E., 39, pp. 1035-1043, Sept., 1951. 



This paper describes a travelmg-wave amplifier in which the electron beam 

 interacts with a spatial harmonic of an electromagnetic wave propagating along 

 an array of resonator slots. The result is a considerable reduction in operating 

 beam voltage for a given physical separation of the circuit elements. This type 

 of amphfier operating at about 1,200 volts has yielded net power gains of about 

 18 db in the 6-mm wavelength region. A magnetic field of about 1,600 gauss is 

 sufficient for proper beam focusing. Aside from small variations of gain with 

 frequency that is caused by internal reflections, the bandwidth is of the order 

 of 3 per cent. 



Form of Transient Currents in Tomnsend Discharges with Metastahles* 

 J. P. MoLNARi. Phys. Rev., 83, pp. 933-940, Sept. 1, 1951. 



The form of the current is calculated for a Townsend discharge stimulated 

 by a pulsed light beam, with particular reference to the current component 

 initiated by metastable effects. The calculation is directed particularl}^ to the 

 development of methods for quantitative interpretation of current patterns 

 observed experimentally. 



Studies of y-Processes of Electron Emission Employing Pulsed Town- 

 send Discharges on a Millisecond Time Scale.* J. P. Molnar\ Phys. 

 Rev., 83, pp. 940-952, Sept. 1, 1951. 



* A reprint of this article may be obtained on request. 

 > Bell Tel. Labs. 



