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BELL SYSTEM TECHNICAL JOURNAL 



zero temperature coefficients, in terms of the ratios of the uncoupled 

 temperature coefficients and the coupHng. 



Referring again to Fig. 6, wo' and coo" represent the values of w' and 

 oi" which would have zero temperature coefficient provided m is 

 greater than n, that is, the temperature coefficient of coi is greater in 

 magnitude than that of C02. Carrying this idea over to the case of 

 the group of circuits for which the curves of Figs. 8 and 9 are drawn, 



TEMPERATURE 



Fig. 12 — Effect of temperature on the angular frequencies of a system of two coupled 

 circuits having temperature coefficients of opposite sign. 



there will be points of zero coefficient in the neighborhood of each 

 coupling point as indicated by the circles on the curves. 



The above conditions for zero temperature coefficient only apply 

 if the coefficient as a function of the tuning be examined in the region 

 of some given temperature. If the temperature is varied over a 

 considerable range a small change in the tuning of both circuits is 

 effected, one having its frequency raised, the other lowered. The 

 result of this tuning on the frequencies of the coupled system can be 

 illustrated by Fig. 12, which shows the tuning with temperature on a 

 magnified scale. In this figure, the lines coi and C02 represent the change 



