ARTICLES BY BELL SYSTEM AUTHORS 483 



sounds from acoustical measurements. Methods based upon analysis, syn- 

 thesis, and vocal tract models are described. Included are the results of pre- 

 liminary measurements on the vowel sounds of 25 speakers. Some of the 

 problems in specifying the vowel sounds as indicated by these results are 

 discussed. 



Protective Grounding of Electrical Installations on Customer's Premises. 

 A. H. ScHiRMER.i A.I.E.E., Trans., v. 69, pt. 1, pp. 657-659, 1950. 



Abstract — The problem of electrical safety in rural areas is one of pro- 

 viding adequate insulation on circuits and equipment, and effective ground- 

 ing and bonding. Providing adequate insulation presents no particular prob- 

 lems. However, there is some confusion as to what constitutes effective 

 grounding and bonding. This paper briefly discusses the various factors 

 which must be taken into account. The discussion is limited to a-c circuits. 



Six-System Urban Mobi'e Telephone Installation with 60-Kilocycle Spacing.* 

 R. C. Shaw,^ p. V. DiMOCK,! W. Strack, Jr./ and W. C. Hunter.^ I.R.E., 

 Proc, V. 38, pp. 1320-1323, Nov., 1950. 



Abstract — This paper describes a 6-system mobile radiotelephone installa- 

 tion in Chicago, operating in the 152- 162 -megacycle band, and using 60-kc 

 spacing of carrier frequencies, rather than the 120-kc spacing of previous 

 practice. The measures required to achieve this frequency saving are de- 

 scribed, including filters and special antenna arrangements at the land trans- 

 mitter, "off-channel squelch" in the land receivers, connection of six land 

 receivers to a common antenna, and other special co-ordinating means. 



Tone Rendition in Photography.* W. T. Wintringham.^ References. I.R.E., 

 Proc, V. 38, pp. 1284-1287, Nov., 1950. 



Abstract — The photographic field is reviewed to find whether the tone 

 rendition of a good picture can be predicted. The television engineer can find 

 no solace in the fact that good photographs were made before measurements 

 were made of the photographic media. He will be thwarted further when he 

 learns that the best print is the result of experienced criticism of a work 

 print. However, the experience of the photographer in obtaining pleasing 

 results in spite of the limitations and distortions of the photographic proc- 

 ess should be useful to the television engineer. 



Ferromagnetic Resonance in Nickel Ferrite.* W. A. Yager.^ J. K. Galt,^ 

 F. R. Merrit,! and E. A. Wood.^ References. Phys. Rev., v. 80, pp. 744-748, 

 Nov. 15, 1950. 



Abstract — ^The ferromagnetic resonance phenomenon in single crystals of 

 NiO Fe203 has been studied at room temperature at 24,000 Mc/sec. Small 



* A reprint of this article may be obtained on request to the editor of the B. S. T. J. 

 1 B. T. L. 



