1076 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1953 



solenoid operated bars is insufficient to support the load and, therefore, 

 if this happens, the bars will yield until the load is taken up by the pole 

 faces of the pull-down magnet. The total drop amounts to 0.180" which 

 then will become the effective air gap at the pull-up magnet pole faces. 

 This is more than ten times the normal gap (O.OIO'O and the pull-up 

 magnet is incapable of restoring the card stack to its normal level. This 

 is despite the fact that when the gap is normal, the pull exerted is in the 

 order of 400 lbs and the breakaway pull is approximately 1000 lbs. Ac- 

 cordingly, mechanical means had to be provided for restoring the stack 

 to normal under this condition. Since this rarely occurs, it was concluded 

 that manual restoration would suffice and a hand crank, together with 

 sundry components, including card lift bails, that are illustrated by Figs. 

 27 and 28 are provided. 



Coding of the cards involves many considerations. It has been men- 

 tioned that a template is used to indicate the holes that should be 

 enlarged and the tabs that should be removed. Obviously, punch and 

 die sets are required to do this. They are provided as components of a 

 tool which is illustrated by Fig. 21. This tool provides a carriage upon 

 which the card to be coded and the template that provides the coding 

 information are mounted in fixed relationship. The carriage may be 

 moved about to effect registration of the holes to be enlarged or the tabs 

 to be removed, with respect to the punches and dies. When enlarging 

 holes, the carriage is moved to a position where a foot treadle operated 

 pilot registers with a hole in the template and then the treadle is de- 

 pressed. The pilot enters the hole in the plate that supports the tem- 

 plate. The hole is close fitting to effect approximate alignment. As the 

 motion progresses a pilot that is part of the punch assembly effects 

 precise alignment between the punch and the hole to be enlarged. This 

 final alignment is made possible by providing for a small amount of 

 float of a card on the carriage. As the foot treadle is depressed further, 

 the punch enlarges the hole in the card. For coding the tabs, a second 

 punch and die set is provided. It is brought into action by a microswitch 

 controlled solenoid that actuates the punch. The carriage referred to is 

 notched along one edge in registration with the tab positions of the 

 template. Wherever the template is notched, the corresponding card 

 tab is to be removed and the carriage is positioned so that these notches 

 successively may be registered with a stylus associated with the solenoid 

 control switch. The carriage then is moved against the stylus and in 

 doing so the switch is operated which causes the solenoid to actuate the 

 punch, thereby clipping off the corresponding tab of the card. In clipping 

 off tabs the punch does not have to be aligned precisely with the tab 



