722 



THIO HELL SYSTKM TECHNICAL JOUKXAL, MAY 1957 



1800 



1600 



1400 



01 



5 



< 1200 



cr 



O 



z 



- 1000 



I— 

 X 



°^ 800 

 O 



^ 600 



CL 



400 



200 



200 



400 - 



to 



< 600 



a. 



o 



- 800 



1000 



D 1200 

 a. 



1400 



1600 



1800 



10 8 642024 68 10 



-« LEFT RIGHT >- 



ARMATURE POSITION IN LINEAR MILS 



Fig. 10 — Spring and magnetic forces on armature of J-7 valve. 



are shown to illustrate the need for these restrictive measures. The need 

 is better appreciated when Fi^'. 10 is (examined. This graph shows the 

 differential pull of the two coils ])lotted against armatiu'c movement for 

 extreme signals and foi' the balanced condition. There is also a line repre- 

 senting the spring force and one representing its reflection. The latter 

 permits direct comparison of the magnitude of the o]:)posing magnetic 

 and spring forces. 



