. The Bell System technical journal . -stal plate by meansof fine These designs are known, respectively, as the Pressure T^peand Wire Supported Type, and will be discussed later under these , there are several details of fabrication common to both typeswhich can best be discussed at this Fig. —Pressure-type holders. Irrespective of the type of mounting, realization of the desired perform-ance in a crystal unit depends to a considerable extent on the processing ofthe quartz plate itself. Previous articles^^ have brought out the signifi-cance of such factors a
. The Bell System technical journal . -stal plate by meansof fine These designs are known, respectively, as the Pressure T^peand Wire Supported Type, and will be discussed later under these , there are several details of fabrication common to both typeswhich can best be discussed at this Fig. —Pressure-type holders. Irrespective of the type of mounting, realization of the desired perform-ance in a crystal unit depends to a considerable extent on the processing ofthe quartz plate itself. Previous articles^^ have brought out the signifi-cance of such factors as the precision of angular orientation and lineardimensions on the fundamental characteristics of the plate. The platemust also be virtually free of impurities or imperfections.^ In the prepara-tion of a quartz plate it must be lapped using increasingly finer abrasivematerials until the final dimensions are reached. Depending upon the typeof crystal unit. No. 400, No. 600 carborundum or finer abrasives are now * A. W. Ziegler, Patent 2,275,122, March 3, 1942. The Use of X-Rays for Determining the Orientation of Quartz Crystals, W. and E. J. Armstrong, , Vol. XXTI, Oct. 1943. ■> Raw Quartz, Its Imperfections and Inspection, G. W. VVillard, , , Oct. 1943. 236 BELL SYSTEM TECH
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