484 BELL SYSTEM TECHNICAL JOURNAL 



maximum stimulation on the basilar membrane and the frequency 

 of the tone producing the stimulation. 



Pick-up for Sound Motion Pictures {Including Stereophonic)} J. P. 

 Maxfield, a. W. Colledge and R. T. Friebus. Although the basic 

 principles underlying sound pick-up for motion pictures have been 

 understood for some time, the ability to carry them out completely 

 in the presence of the requirements of artistry, photography, lighting, 

 etc., has constituted a difficult problem. The paper discusses some 

 of these problems, particularly with respect to the acoustics of produc- 

 tion sets and scoring stages. The problems of stereophonic repro- 

 duction are also discussed in some detail. 



Practical Application of Telephone Repeaters and Carrier Telephone 

 Systems} J. A. Parrott. The paper discusses engineering problems 

 in the application of telephone repeaters and carrier systems with 

 which railroad communication engineers recently have been particu- 

 larly concerned. The first part of the paper deals with crosstalk, 

 noise, balance and overloading considerations in the design of re- 

 peatered circuits, particularly from the standpoint of selecting the 

 locations of repeaters to obtain the most satisfactory results on existing 

 lines. The importance of securing test data on the wire facilities to 

 aid in this design work as well as to serve as a guide in improving 

 circuit conditions is emphasized. 



The second part of the paper briefly discusses the application of 

 the HI carrier telephone system and provides transmission data for 

 the preliminary design of the layout of such systems. The Type D 

 and KIO carrier transpositions are described and features of particular 

 interest in their possible use on railroad facilities are discussed. 



Sorption of Water by Rubber.^ R. L. Taylor and A. R. Kemp. 

 The effect of several variables on the rate of sorption of water by 

 rubber is discussed. Expressions based on short-time immersion tests 

 are derived which permit calculation of the water content after an 

 extended period of immersion under fixed conditions of temperature 

 and vapor pressure. A sorption coefficient by which one material 

 may be compared with another is suggested, and its application to 

 practical problems is considered. 



3 Jour. S. M. P. E., June 1938. 



* Proc. Assoc, of Amer. Railroads, Telegraph and Telephone Sec, October 1937. 



^ Indus. & Engg. Chemistry, April 1938. 



