Developments in communication materials

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 engineering 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 office wiring treated to improve their electrical insulating quality and non-ferrous metals of more uniform characteristics. Problems involving the use of duralumin for radio broadcasting transmitters and the light valve used in sound pictures are also described. Particular emphasis is laid on the benefits resulting from the continuous 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.