872 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1952 



pattern of the CSP network for the country as seen from the CSP 

 concerned and are interconnected in a pattern of progression correspond- 

 ing to the fixed order of alternate route selection. Group busy leads from 

 the toll line groups are connected to the contacts of the relays in such a 

 manner that if a group is busy the relay corresponding to the next choice 

 route in the chain will be operated. In this way the lowest choice route 

 having an idle circuit will be speedily selected without testing individual 

 trunks of separate groups. The decoder learns from the translator which 

 relay in the array to operate first and the choice of the best route a\'ail- 

 able follows automatically. The principle will be readily understood by 

 reference to the simplified sketch in Fig. 3. Contacts not shown on the 

 relaj^s cause the translator to select the route corresponding to the last 

 relay operated in the chain. 



5. Translators 



The magnitude of the translating job for nationwide dialing led to the 

 decision to develop a new translator operating on a principle radically 

 different from that employed in other crossbar systems. In previous 

 systems translation is done by relays. The code digits - never more than 

 three - operate a group of relays which cause a single terminal corre- 

 sponding to the code to be selected. A cross-connection is made between 



HIGH-USAGE ROUTES 



FINAL ROUTES 



ALL 



TRUNKS BUSY 



INDICATION 



I -INDICATION FROM TRANSLATION OF THE FIRST ALTERNATE ROUTE 

 '-INDICATION THAT ALL TRUNKS IN THE GROUP ARE BUSY 



Fig. 3 — Alternate route array for the decoder at a sectional center. 



