ABSTRACTS OF TECHNICAL ARTICLES 513 



which may be fixed in the production process at values between 3 and 1,000 volts 

 and (e) ability to operate at ambient temperatures as high as 300°C. 



Hard Rubber. H. Peters^ Ind. and Eng. Chem., 44, pp. 2344-2345, 

 Oct., 1952. 



As judged by the literature, the general trend during the past year on the 

 subject of hard rubber has been toward de-emphasis of fundamental research and 

 more emphasis on use. Plastics, through substitution, continue to make gains 

 in the field of hard rubber. A renewed interest is again shown in the use of latex 

 ebonite for industrial applications. The patent situation appears to be unusually 

 active and the interest in sjTithetic hard rubbers continues to increase. 



Application of Information Theory to Research in Experimental Pho- 

 netics. G. E. Peterson^ Jl. Speech and Hearing Disorders^ 11 j pp. 175- 

 188, June, 1952. 



Principles of Zone-Melting. W. G. Pfann^ Jl. of Metals, 4, pp. 747- 

 753, July, 1952. A.I.M.E. Trans., 194, pp. 747-753, 1952. (Monograph 

 2000). 



In zone-melting, a small molten zone of zones traverse a long charge of alloy 

 or impure metal. Consequences of this manner of freezing are examined with 

 respect to solute distribution in the ingot, with particular reference to purifica- 

 tion and to prevention of segregation. Results are expressed in terms of the 

 number, size, and direction of travel of the zones, the initial solute distribution, 

 and the distribution coefficient. 



Nonsynchronous Time Division with Holding and with Random Sampl- 

 ing. J. R. Pierce^ and A. L. Hopper^. I.R.E., Proc, 40, pp. 1079-1088, 

 Sept., 1952. (Monograph 2041). 



There is a general tj-pe of system in which an indefinitely large number of 

 transmitters can have access to anj^ of an indefinitely large number of receivers 

 over a medium of limited bandwidth. In these systems, signal-to-noise ratio goes 

 down as more transmitters are used simultaneously. This paper describes a 

 particular system which sends samples by means of coded pulse groups sent at 

 random times. The signal-to-noise ratio is good in the absence of interference 

 and the effect of interference is minimized by holding the previous sample if a 

 sample is lost. An experimental sj'stem worked satisfactorily and gave close to 

 the predicted signal-to-noise ratio. Such a system might be used to provide com- 

 munication and automatic switching in rural telephony, or for other applica- 

 tions. 



Fundamental Plans for Toll Telephone Plant. J. J. Pilliod^. A.I.E.E., 

 Trans., Commun. & Electronics Sect., 2, pp. 248-256, Sept., 1952. (Mono- 

 graph 2015). 



^ Bell Telephone Laboratories. 



2 American Telephone and Telegraph Company. 



