MEASUREMENTS AT TELEPHONIC FREQUENCIES. 109 



impedance is 0^ = 464.7 \- 74°. 25. At c = o, the vector impe- 

 dance is 0L = 266.2 ^ 55°.6 ohms. The angle mol in Fig. yb is 

 the same (19°) as the angle MOL in Fig. 8. As c is increased from 

 c-^o to c=co, the vector impedance pursues the wide circle 

 LPGM. 



Fig. 8. Locus diagram obtained by inversion from Fig. 7b, and showing the 

 variation of total main-circuit impedance of the main-circuit of Fig. 7a. 



The explanations for these interesting circular graphs of Figs. 

 yb and 8, appear step by step in Fig. 9. Fig. ga shows the vector 

 admittance of the Ic combination in Fig. ya, as taken between the 

 points qq' in the main circuit. 01, Fig. ga, is the fixed admittance 

 of the coil /, Fig. ya, at the constant impressed frequency of 525-^' ; 

 namely 0.4656 — 74.343 = 4.369 "\ 83°. 53' millimho. The admit- 

 tance of the condenser c will be jcm. The vector sum of 01 and ;Vw 

 will evidently lie on the straight line Int, as c varies from o to co. 

 The corresponding impedance of the Ic combination, between points 

 qq' in the main circuit, Fig. ya, will be the vector reciprocal of the 

 straight line locus Im, Fig. ga, and must therefore be a circle, as has 



