534 



BELL SYSTEM TECHNICAL JOURNAL 



If it were not for the decrease in activity of the period with the 

 negative temperature coefficient it is to be expected that the crystal 

 frequency, instead of "hopping," would continue to decrease with 

 increase in temperature. In some instances (for low order of har- 

 monics) the crystal frequency will decrease for a few degrees, and it 



3200 



2800 



O 



< 2000 



400 



CURVE A 8TH. HARMONIC 

 CURVE B 5TH. HARMONIC 



24 



32 



40 48 56 



TEMPERATURE — DEC. CENT. 



Fig. 16 — The frequency change with temperature of two parallel cut crystals of 

 different width. 



Curve A region of eighth harmonic 



(width = 32.0 mm.) 

 Curve B region of fifth harmonic 

 (width = 19.35 mm.) 

 The other dimensions of the plates are identical. 



