288 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



Lo 



"7GAPS 



(b) 



AIR GAP LENGTH 



Fig. 12 — Inductance adjustment with partially compensating air gaps. 



proximately directly as the ratio of air gap area to magnetic core area. 

 Adjustment by variation of the area of the gap, therefore, is not subject 

 to the nonlinearity that results from manipulating the air gap length. 

 A simple method for providing adjustment by varying the effective area 

 of the air gap is shown in Fig. 13. As one shell is rotated with respect to 



AIR 

 GAP" 



Fig. 13 — Inductance adjustment by variation in air gap area. 



