1064 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1953 



Portable test set. 



It was estimated that a card translator, on the average, would be 

 called upon to function from twenty to thirty million times a year. 

 Accordingly, provision for direct-acting, high-speed, long-life and readily 

 replaceable components became another objective. 



A further objective was the provision of means for reading the routing 

 information without mechanically contacting the cards, as for instance 

 by utilizing photo-detection circuirts, such as have been referred to, as 

 it was rea-soned that in this way reliability over an extended period could 

 best be assured. 



ELECTRO-MECHANICAL DESIGN 



Phototransistors are utilized as the photo-sensitive elements, the light 

 source is a standard projection lamp, the light beams are modulated and 

 then directed through the card formed tunnels by dual collimating lenses 

 and then upon emission from the card stack are focused on the photo- 

 transistors. (See Figs. 17 and 18.) To a large extent the card, which is 



