528 



BELL SYSTEM TECHNICAL JOURNAL 



Mr. W. A. Marrison of the Bell Telephone Laboratories first 

 suggested that low temperature coefficients could be obtained with 

 parallel cut crystals by utilizing the coupling of two modes of vibration 

 having individual coefficients of opposite sign. Several of this type 

 of low temperature coefficient crystals were produced by Marrison 



1800 



1600 



1400 



'^, 1200 



600 



34 38 42 



TEMPERATURE DEC. CENT. 



Fig. 11 — The frequency change of a 32 x 47 x 2.760 mm. parallel cut 

 crystal with temperature. 



and are described in his concurrent paper "A High Precision Standard 

 of Frequency." 



If Heising's coupled circuit analysis is extended to include the 

 effect of temperature and the proper temperature coefficients with due 

 regard to relative magnitude and sign are identified with each circuit, 

 the change in temperature coefficient with dimensional ratio and 



J 



