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BELL SYSTEM TECHNICAL JOURNAL 



back half of the plate. This discussion relates only to the case of the high 

 frequency shear commonly assumed to be a single shear along the length and 

 thickness of the plate. Similar statements can be made if we consider 

 the high frequency shear as being along the width and thickness. 



m = 1 

 n = 1 

 P =2 



Fig. 6.5 — Motion of a plate in high frequenc}^ shear. 



6.24 Type of Motion for Some Standard Filter and Oscillator Plates 



To get a more complete picture of the applications of the various types 

 of motion, we will now take specific cases. The various crystals as com- 

 monly used for oscillators or filters are shown in Fig. 6.6. At the top of Fig. 

 6.6 are shown the various types of shear plates with their relative position 

 with respect to the crystallographic axis. 



The AT and BT plates are termed high frequency shear plates and the 

 motion associated with them is that of a length-thickness shear as shown in 

 Fig. 6.5. Their use is found for the control of radio frequency oscillators in 



