Measurement of Frequency of Electrical Oscillations. 291 



the period of interruption of the buzzer. Every position 

 of the maxima on the scale C 2 defines thus the frequency of 

 a certain harmonic of an oscillation, whose fundamental 

 is given by the number of the buzzer interruptions per 

 second. 



Let n be the number of the interruptions per second of 

 the buzzer, v Y the natural frequency to be measured of the 

 circuit II in a certain position of the condenser C 2 ', v 2 a 

 higher frequency of the circuit II in another position of 

 the condenser C 2 ", k a number indicating which harmonic 

 v, is in relation to the fundamental n, and s the number 

 of maxima s observed while moving the condenser C 2 from 

 the position G 3 ' to C 2 '' ': — 



v\ = rc«, . (1) 



v 2 = n(/e+s) (2) 



"1 = -^-; s = «C-l-l\ 



Prom (1), v 1 



K — . 



n 



n \vi J 



v l = s.n. (3) 



(S- 1 ) 



By counting the number of maxima heard in the 

 telephone while moving the condenser C 2 from C 2 ' 

 to 0" s is found ; n can be measured by any known 

 acoustical or optical method; it remains to find the 



ratio — . The most practical way is to choose the second 



position of the condenser 2 ", not arbitrarily, but to 

 determine it so that the natural frequency of circuit II 

 for that position shall be a known multiple of that to be 

 measured (CV). This position can be easily found by 

 excitation of the circuit II from a separate source of 

 oscillations energised by an electric arc or thermo-ionic 

 valve and containing usually harmonics of its fundamental 

 frequency. 



The absolute measurements were accomplished in the 



U2 



