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BELL SYSTEM TECHNICAL JOURNAL 



A T and BT crystals can control considerably more powerful oscillators 

 without danger of the crystals breaking than can the X or Y cut 

 crystals. The frequency spectrum of an ^7" cut plate ground down 

 from a large ratio of dimensions to a smaller one is shown on Fig. 5. 



2100 



2000 



o 



z 

 o 



O 1 800 

 10 



9 10 11 12 



LENGTH OF X AXIS IN MILLIMETERS 



13 



Fig. 5 — Frequency spectrum (dots) for an AT plate as a function of ratio of length 

 to thickness. The dashed lines represent calculated flexural vibrations. The whole 

 line is the principal shear mode. The dot dash lines are other shear modes. 



Most of the prominent frequencies can be identified as shear frequencies 



of the type discussed in a previous paper ^^ and harmonics of flexure 



^""Electrical Wave Filters Employing Quartz Crystals as Elements," W. P. 

 Mason, B. S. T. J., July 1934, page 446. The verification was made by R. A. Sykes 

 who kindly supplied Fig. 5. 



