The Evolution of Inductive Loading for Bell System Telephone Facilities

P A R T IV: CABLE LOADING COIL CASES General Up to this point this review of coil loading has been primarily in terms of transmission features of the loading systems and the coils, and development economics, and for this reason the references to potting developments have been brief, so as to minimize diversions from the main theme. A complete chronological review of all important aspects of the potting development work would require much more space than is available for this present article. On the other hand, because* of the substantial importance of the potting developments in the economics of loading, more should be said than was included in the brief references in Parts II and I I I of the story. This particular part of the review accordingly describes the more important high spots of the potting developments. It is limited to cable loading coil cases because of the early obsolescence of open-wire loading. The discussion is in terms of the changes from time to time in the various important design features, as indicated by the side headings and paragraph headings, and is thus a departure from the individual project-description procedure followed in other parts of the review. At this point it should be emphasized that the work on the cases, which has been more nearly continuous than that on the coils, has kept pace in design ingenuity with the work on the coils, and has been very much more than the mere accommodation of the case designs to the changing sizes of the loading coils and of the loading complements.