CARD TRANSLATOR FOR NATIONWIDE DIALING 1075 



The weight of the stack normally is borne by the latches via the code 

 select bars, but as the time approaches for their operation the stack is 

 elevated by energization of the pull-up magnet and the latches thereby 

 are freed for fast operation. 



Separation of the cards just prior to dropping a selected card is effected 

 by the pull-up and pull-down magnets. These magnets induce like 

 magnetic poles in corresponding portions of all the cards and the parti- 

 tions of the card cage as may be deduced by reference to Fig. 20 and the 

 resulting mutual repulsion causes the cards to separate as may be noted 

 by reference to Fig. 26. This assures free action of the selected card. The 

 pull-up magnet is deenergized when the required code select bars are 

 checked down. The pull-down magnet is maintained energized to assist 

 the dropping of the card. 



The nominal initial jump of the card stack, or the separation between 

 the top of the card stack and the pull-up magnet pole faces is nominally 

 0.016". When the magnet is energized the stack ''jumps" to the pole 

 faces in about 15 milliseconds which is fast considering that the load 

 may be as much as 100 pounds. 



The nominal drop of the selected card is 0.180". Accordingly, the theo- 

 retical free fall time is 33.2 milliseconds and the terminal velocity is 

 12.7" per second. However, under working conditions, the selected card 

 does not fall freely and except for the added pull of the pull-down mag- 

 net, the drop time would average about 40 milliseconds. The pull-down 

 magnet is capable of reducing the drop time in a working translator to 

 as little as 16 milliseconds or approximately one-half the theoretical 

 free fall time with a measured terminal velocity as high as 35" per 

 second. Should this speed be permitted, the impact forces developed 

 would be of sufficient magnitude to cause the tabs of the cards to mush- 

 room to an unworkable degree and to cut through the nylon surfacing 

 of the pole faces of the pull-down magnet in less than one million opera- 

 tions. Under the restraining influence of the card support bars, the 

 drop time averages 33 milliseconds or a reduction of approximately 20 

 per cent with respect to the unaided operate time and the maximum 

 terminal velocity measured has been 20" per second. Working at this 

 speed, there is virtually no mushrooming during the normal life of the 

 card and the nylon facing survives well over 100,000,000 operations, 

 thus showing a gain attributable to the use of card support bars of more 

 than 100 to 1. 



Inadvertent dropping of all cards of the stack is possible although 

 highly improbable. It can happen if the stack is released from its sus- 

 pended position when the latches are not in a position to support the 

 code select bars. The combined strength of retractile springs of the 



