1082 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1953 



fastened to the bottom of the bars. Both the top and the inside surfaces 

 referred to are faced with nylon. The combination stop and guide de- 

 tails are located so that the top surface of the solenoid operated bars lies 

 about 3^4" below the pole faces of the pull-down magnet when the bars 

 are fully depressed. This under flush condition is necessary to assure that 

 the pole faces act as the down-stop for the selected card as is intended. 



CENTER GUIDES 



To maintain the intended vertical disposition of the solenoid operated 

 bars, additional comb-like guides are provided that engage the bars at 

 their center near the bottom edge. Actually they engage the graphitized 

 phenolic linin details that are inserted at the center of the bars. This 

 arrangement of the comb guides provides triangularly disposed guidance 

 that affords both transverts and vertical stability with minimum working 

 friction. 



OFF-NORMAL CONTACTS 



It is important that all of the code select bars necessary for selecting 

 the required routing card be checked down before proceeding further 

 with a translation and it is equally important that after translation 

 they all be checked up before proceeding further towards restoration 

 of the translator to normal. Off -normal contact springs that are operated 

 by the bars are provided for this purpose. They are mounted at the light 

 source end of the bars as indicated in Fig. 18. They also are illustrated by 

 Fig. 30, and from this illustration it will be noted that off -normal con- 

 tacts also are provided for the card support bars. These latter contacts 

 close as the bars are operated to start timing of the "no card" timing 

 circuit. When the card support bars are released, their off -normal con- 

 tacts control the circuit of the card-support lift-bar magnets. This is a 

 desirable arrangment because these magnets are required to supplement 

 the solenoid retractile springs only as the card-support life-bars approach 

 their upper stop position where they engage any cards that may be 

 tilted. Late energization of these magnets prevents the development of 

 high .tab impact forces. 



LATCHES 



The latches are magnetically operated to free the solenoid operated 

 bars and are spring returned to their bar engaging position. Four are 

 provided : two at each end of the bar array, one for the left-hand group- 

 ing and the other for the right hand. Accordingly, each has to be capable 



