1042 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER, 1953 



the desired point in the area. To other areas there may be only one 

 route and in this case the area code will suffice. 



The provision of facilities for the translation of six digits greatly 

 affected the design of the switching system for the nationwide dialing 

 CSP offices. It led to the development of the basically new card trans- 

 lator. In previous toll common control systems translation is done by 

 means of relays. The code digits, never more than three of them, re- 

 sulted in the operation of groups of relays in certain combinations and 

 led to the eventual operation of a route relay for the particular com- 

 bination of code digits. This route relay with cross-connecting facilities 

 from its contacts is used for the identification and selection of trunk 

 groups and other information as might be required for the particular 

 code routings. To change a routing with this system of translation re- 

 quired the removal and reconnection of many cross-connections. 



With the nationwide dialing plan in operation, routing changes or 

 opening of new offices in one part of the country will necessitate trans- 

 lator changes in many offices, some of them far removed from the scene 

 of the event that forced them to be made. The changes in any one CSP 

 may, therefore, be frequent under certain conditions, and to make them 

 by running cross-connections would be cumbersome and expensive. The 

 new translator uses punched cards instead of relays making it possible to 

 effect changes by the simple process of removing old cards and insert- 



INCOMING 

 LINK FRAMES 



OUTGOING 

 LINK FRAMES 



INCOMING 

 TOLL LINES < 

 OR TRUNKS 



TANDEM TRUNK 



u 



OUTWARD 

 TOLL 

 BOARD 



CALLING 

 SUBSCRIBER 



SENDER 

 LINK FRAME 



SENDER 



^i;- 



DECODER 

 CONNECTOR 



MARKER 

 CONNECTOR 

 o 



TO 

 DISTANT 

 ' TOLL 

 OFFICES 



TO LOCAL 

 OFFICES 



TRUNK 



BLOCK 



CONNECTOR 



FOREIGN 



AREA 



TRANSLATOR 



DECODER 

 TRANSLATOR 



-FOREIGN AREA 

 TRANSLATOR 

 CONNECTOR 



Fig. 2 — Schematic diagram of crossbar switching system for CSP's. 



