1044 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER, 1953 



registered in the sender on a two-out-of-five basis and the leads from the 

 sender will cause the select bars to be operated. If the card represents 

 an ordinary three digit code, all the tabs will be cut off except two 

 each for the A, B, and C groups of tabs, and, for reasons that will 

 be discussed later, two of the four CG tabs, card group, will also be 

 removed. In addition, either the VO or NVO tab may be removed. The 

 VO and NVO tabs are used when the group of toll lines over which the 

 call will be routed is divided into one sub-group of a transmission grade 

 suitable only for terminal traffic (NVO, meaning ''not via only") and 

 another subgroup for either terminal or switched-thru traffic (VO mean- 

 ing "via only"). If the card represents a six-digit code, two tabs will be 

 left in each of the six code digit positions and a different pair of card 

 group tabs will be used. 



The cards, then, are in different groups and are selected by combinations 

 of code select bars together with the card group select bars. As noted 

 there are four of these card group bars, CGO, CGI, CG2 and CG4. 

 They are used in the six possible combinations, two at a time as follows : 

 For the regular three-digit code cards CGI and CG4, for the regular 

 six-digit code cards CG2 and CG4; the other four combinations CGO 

 and CGI, CGO and CG2, CGI and CG2, and CGO and CG4 are used for 

 selecting the four groups of alternate route cards, which may be of the 

 three-digit or six-digit variety. 



CODE CAPACITY 



The card translator by means of the code select bars and card tabs 

 provides facilities for a great number of different codes and routings. 

 There are 40 select bars provided, 36 of these are used in the combina- 

 tions as has been described, two are reserved for possible future use and 

 the remaining two are used for aligning the cards as will be discussed 

 later. The total possible card code combinations is sufficient for growth 

 in nation-wide diaUng for the foreseeable future. 



TRANSLATOR CARD CAPACITY 



In some CSP offices there will be many thousands of cards for the 

 destinations to be reached. It was not mechanically practicable to design 

 a single translator capable of accommodating all these cards and more- 

 over it would not have been economical, particularly for many of the 

 smaller CSP offices. Also for service hazard reasons and to provide for 

 the simultaneous translation of several calls, needed to handle traffic 

 during heavy load periods, more than one translator is required in a 



