1020 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER, 1953 



(B4\ 



(a) RINGDOWN 

 OPERATION 



q regional center 

 ^Iprimary outlet 

 • toll center 



A5 



(b) NATIONWIDE 

 TOLL DIALING 



FINAL GROUPS □ ''Iffg^ ^^^ O PR'^ARY OUTLET 



MU ronnp. A SECTIONAL ^ ^^^^^^ ^^^'"^^ 

 HU CROUPS ZA CENTER « JOLL CENTER 



Fig. 1 — Typical intertoll trunk networks. 



