Abstracts of Technical Articles from Bell System Sources 



Protection Features for the Joint Use of Wood Poles } J. O'R. Cole- 

 man and A. H. Schirmer. The paper reviews the historical develop- 

 ment of joint use and the general results to date of studies of protective 

 problems of lower and higher voltage joint use. The safety features 

 are reviewed from the standpoint of (1) subscribers' premises, (2) em- 

 ployees, and (3) telephone plant. Characteristics of equipment of 

 power and telephone plant as far as they relate to this problem are 

 given. The various factors which determine magnitude and duration 

 of the current and voltage in the telephone plant resulting from a con- 

 tact with power conductors are discussed. Improved methods for 

 obtaining safety under various conditions, where higher voltage joint 

 use is found to be the best over-all solution, are described. 



High-Speed Motion Picture Photography Applied to Design of Tele- 

 phone Apparatus? W. Herriott. High-speed motion pictures are 

 employed at Bell Telephone Laboratories as a visual aid in the study 

 of problems associated with the design, manufacture, and testing of 

 telephone apparatus. A new high-speed camera of the optical com- 

 pensator type operating at 4000 pictures per second is described, and 

 its application to the study of problems associated with telephone 

 apparatus is discussed. 



Mass Ratio of the Carbon Isotopes from the Spectrum of CN.^ F. A. 

 Jenkins and Dean E. Wooldridge. With a source containing carbon 

 enriched about ten times in C^^, the violet CN bands have been photo- 

 graphed with a dispersion of 0.63A/mm. Measurements are given of 

 the lines of low rotational quantum number in the 0,0, 0,1 and 0,2 

 bands of C^^ N"^"*, as well as of C^^ N^"*. The vibrational constants of the 

 normal states of both molecules are accurately determined, and give a 

 value of the isotope mass coefficient p = oj^/w, of 0.97898 ± 0.00002, 

 corresponding to a mass for C^^ of 13.0088. This is in essential agree- 

 ment with the mass-spectrograph value, and it is shown that the finer 

 corrections to the isotope effect are negligible in this case. 



» Elec. Engg., March 1938. 



2 Jour. S. M. P. E., January 1938. 



3 Phys. Rev., January 15, 1938. 



319 



