1090 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1953 



magnet will be incapable of lifting the card stack because of the ma- 

 terially increased airgap and, therefore, the translator will be rendered 

 inoperable. However, the bails provide a convenient means for clearing 

 the trouble because the top notches in the cards are so located and are 

 of such a size that they may be engaged by the bails even when the cards 

 are at the pull-down magnet level and the lift motion is sufficient to 

 permit the latches again to assume their card stack supporting role. 



REMOVAL OF CARDS 



To remove the cards, the pull-up magnet must be lifted sufficiently to 

 permit of the cards being raised above the lower card guide bar. In 

 addition, the upper card guide bar must be lifted clear of the stack. The 

 crank referred to may be used to effect the required action. The upper 

 card guide bar is raised by rotating the crank beyond the position re- 

 quired to raise the pull-up magnet whereupon a cam of the internal 

 peripheral shell type engages mechanism adapted to lift the guide bar 

 while the pull-up magnet dwells in the elevated position already effected. 

 The mechanism referred to is illustrated schematically in the Figs. 

 27 and 28. 



Cams, locking pawls, and associated circuitry cooperate to prevent 

 operation of the crank while the translator is in service, to limit to the 

 necessary extent the amount that the crank may be turned when 

 removing the dynamic unit or alleviating a card crash and to permit 

 of its being turned sufficiently further to elevate the upper card guide 

 bar to clear the cards when they are to be removed or are being loaded. 

 Study of related figures will make clear the mode of operation of the 

 elevating mechanism. 



PULL-UP AND PULL-DOWN MAGNETS 



These magnets (see Fig. 18) are of the eight coil common pole type. 

 They differ principally in that the cores for the coils of the pull-up mag- 

 net are laminated to provide for fast operation as is required. The 

 operate and release timing of the pull-down magnet is such that its 

 cores need not be laminated. 



It is of vital importance that all of the coils of the magnets are 

 effective as otherwise some of the cards may not be elevated when the 

 latches are called upon to operate, or the cards may not fall reliably. 

 Accordingly, a slave relay is used in series with each of the coils and if a 

 relay fails to operate, thereby indicating possible magnet coil failure, the 

 trouble recorder is called into action and steps are taken to clear the 

 trouble. 



