290 



THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



Fig. 14 — Magnetic variometer. Inductance adjustment by variation in mutual 

 inductance. 



CONCLUSION 



The combined magnetic and mechanical characteritics of ferrite per- 

 mit the design of inductors superior to those using metallic cores in at 

 least three important respects: 



1. Higher values of Q are obtainable than have ever before been prac- 

 ticable. In the range from about 50 to 200 kc, frequently used for tele- 

 phone carrier, it is very difficult to realize a Q above about 300 in a 



