. The Bell System technical journal . materials, it willbe necessary to select a few typical items of interest. The itemsselected deal primarily with the telephone problem as this is, at thepresent time at least, the largest single factor in the communicationsgroup. The subject may be divided broadly into insulating materialsand metallic materials. Insulating MaterialsPhenol FiberConsidering first sheet insulating material, we have been using theterm phenol fiber to cover such materials as bakelite-dilecto, mi-carta, formica and similar fibers made by various fiber is used
. The Bell System technical journal . materials, it willbe necessary to select a few typical items of interest. The itemsselected deal primarily with the telephone problem as this is, at thepresent time at least, the largest single factor in the communicationsgroup. The subject may be divided broadly into insulating materialsand metallic materials. Insulating MaterialsPhenol FiberConsidering first sheet insulating material, we have been using theterm phenol fiber to cover such materials as bakelite-dilecto, mi-carta, formica and similar fibers made by various fiber is used extensively in telephone apparatus. One of itsapplications is in the sequence switch which has insulators alternatingwith conducting segments, as shown in Fig. 1. The sequence switch,which is used in the dial system, draws out an arc when in operationwhich sometimes causes carbonization of the insulators. In some casesa hole was burned through the insulator and in other cases the arc was DEVELOPMENTS IN COMMUNICATION MATERIALS 239. Fig. 1—Sequence switch, used in dial system.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
