The Bell System Technical Journal 



April, 1930 



Developments in Communication Materials^ 



By "WILLIAM FONDILLER 



The subject of engineering materials is one of increasing importance, as is 

 evidenced by the expenditure of over a half billion dollars annually in new 

 construction by the Bell System. This has led to the concentration of the 

 research and engineering work on materials in a group devoted particularly 

 to this field of activity. Studies of the chemical and physical properties of 

 materials must be combined by the materials engineer with a knowledge of 

 the operating requirements of telephone apparatus. 



The paper covers broadly the materials used in communication engineer- 

 ing and gives instances in which the needs of the telephone plant imposed 

 requirements which were not satisfied by commercially available materials. 

 Some of the instances cited are phenol fiber having improved resistance to 

 arcing for use in sequence switches; a composite molded plastic for use in 

 terminal strips; textile materials for central ofilice wiring treated to improve 

 their electrical insulating quality and non-ferrous metals of more uniform 

 characteristics. Problems involving the use of duralumin for radio broad- 

 casting transmitters and the light valve used in sound pictures are also de- 

 scribed. Particular emphasis is laid on the benefits resulting from the con- 

 tinuous research in magnetic materials which have produced successively — 

 powdered electrolytic iron cores for loading coils, permalloy, and recently 

 perminvar. 



Summing up, the work on materials has resulted in benefits along two 

 general lines: 



1. Improvement in quality of commercial materials. 



2. Discovery or development of valuable new materials. 



THE subject of this paper, "Developments in Communication 

 Materials," perhaps needs some definition with the rapid addition 

 of new fields to the pioneer arts of telegraphy and telephony. Today 

 we must include high frequency wire telegraphy and telephony by 

 means of carrier currents, radio, telephotography, television and, in a 

 sense, sound pictures. All of these modes of communication of intelli- 

 gence are characterized by the use of electrical means for the transfer 

 of the signal, sound or scene to distant points, or their recording. 



Up to about ten years ago the average manufacturer left to his 

 designing engineer the problem of selecting and testing the materials 

 which were to be embodied in a design, and he in turn was dependent 

 on the manufacturers of raw materials as to the variety and quality 

 of the materials available. Without depreciating the ability or ini- 

 tiative of manufacturers of engineering materials, it will be evident that 

 the special needs of a particular industry would, in general, not be as 

 fully appreciated by an outside manufacturer as by an engineer working 



1 Presented before A. I. E. E. on November 13, 1929. 



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