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XXVII. The Mandelstam Method of Absolute Measurement of 

 Frequency of Electrical Oscillations. By J. Tykocinski- 

 Tykociner, late Manager of the Radio Department of the 

 Siemens and Halske Works at Petrograd *. 



DURING- the summer of 1915 a considerable number 

 of wave-meters for radio-stations had to be calibrated 

 in the Radio Department of the Russian Siemens and Halske 

 Works in Petrograd, taken under the control of the Russian 

 Government. The comparison of wave-meters calibrated by 

 usual methods by different firms or by the Russian Chamber 

 of Measures and Weights showed large discrepancies. 



To enable a larger number of stations to work with each 

 other without interference, not only has sharp tuning to be 

 applied but the precise setting of the radio apparatus for a 

 given wave-length is of paramount importance. A reliable 

 method of wave-measurement reduced to the use of the 

 simplest standard becomes of great necessity. 



Dr. Mandelstam, chief expert of the Works' Research 

 Department, investigating the behaviour of high-toned 

 buzzers used at that time for generating high-frequency 

 oscillations, for measurements and testing purposes, found 

 that oscillations in a circuit energised by a buzzer do 

 not depend solely on its capacity and inductance, but 

 depend also upon the frequency of the pulsating current 

 delivered by the buzzer, and to a large extent upon the 

 character of its interruptions. 



Mathematical analysis of the phenomena showed that 

 a buzzer, because of the steepness of the curve A (fig. 1), 



Ffo. 1. 



characterising the interrupting current, can be made, in con- 

 nexion with another circuit, a source of trains of oscillations 

 possessing a wide scale of frequencies. The amplitudes of 

 the variety of oscillations obtained are not equal for all 



* Communicated by Dr. L. Silbersteiu. 

 Phil. Mag. S. 6. Vol. 39. No. 231. March 1920. U 



