1084 THE BELL SYSTEM TECHNICAL JOUKNAL, SEPTEMBER 1953 



load and to do so with a small diameter solenoid. Magnetic cross-fire 

 possibilities born of the close mounting conditions required also had 

 to be contended with. Regarding diameter limitations, it will be recalled 

 that the tabs of the cards are on ^g'' centers and that five solenoids 

 are grouped in stagger arrangement. Thus six positions or five spacings 

 have to be considered and, therefore, the diameter of the solenoids has 

 to be less than ^Jie"- This is very small considering what the solenoids 

 have to do, but satisfactory performance was achieved by the use of 

 solenoids of which Fig. 33 is representative. The coil tube is made from 

 beryllium copper because of its high resistivity, resistance to corrosion 

 and its ability to resist wear. The main body of the operating plunger is 

 surfaced with a heavy plating of chromium. The plunger then is ground 

 to size, lapped and buffed to provide a very smooth surface. The blade- 

 like extension that is secured to the main body of the plunger for cou- 

 pling purposes is made from steel. It is hardened, ground and polished 

 to assure long life. The fixed plunger is adjustable axially so that a 

 small but definite operated gap may be provided as otherwise mush- 



CONTACT ACTUATING 

 ARM 



SUPPORT BLADE 



Fig. 31 — Code select bar latch. 



