AUTOMATIC TOLL SWITCHING SYSTEMS 



865 



Assiinui an outwaid opciator in Atlanta has received a station-to- 

 siation call lor a suhscrihcr in iMonticollo, INTaino, whosc^ inimhor is 

 AC'aileniy 4-2345, Ihal Monticcllo is a tiihutary of ilouUoii, a slx^p-hy- 

 step TC, that Bangor is a stop-hv-stcp TO scrxing Houlton as its home 

 TO and that the circuit groups pi'ovidod are as indicated in Fig. 2. The 

 (lott(Ml lines represent high usage groups and the solid lines hnal groups. 



The Atlanta operator plugs into a tandem tnnik to the toll crossbar 

 system in Atlanta, thereby causing a sender to be attached to the trunk 

 through the sender link frame. This causes a lamp signal to l)e displayed 

 to the operator, indicating that she may key the number. She keys 

 207-AC4-2345 plus a start signal (signifying end of keying) into the 

 sender and leaves the connection to handle other calls. She will give this 

 call no fiu'ther attention until the lamp associated with the cord circuit 

 usetl in establishing it signifies either by flashing that the call was not 

 completed due to a busy condition of the called line or to circuit conges- 

 tion, or by going dark that the called subscriber has answered and she 

 should start timing the call. 



As soon as the area code, 207, is received by the sender it calls for a 

 decoder and gives it the code. The decoder, by means of a self-contained 

 translator finds that the area code is sufficient for routing purposes, that 

 the fii'st choice route is by way of Boston, the second New York and the 

 final St. Louis. Without consulting other circuits it will know in which 



INCOMING 

 LINK FRAMES 



OUTGOING 

 LINK FRAMES 



INCOMING 

 TOLL LINES< 

 OR TRUNKS 



TANDEM TRUNK 



OUTWARD 

 TOLL 

 BOARD 



® 1 



CALLING 

 SUBSCRIBER 



SENDER 

 LINK FRAME 



^t- 



DECODER 

 CONNECTOR 



MARKER 

 CONNECTOR 



TO 

 v DISTANT 

 '' TOLL 

 OFFICES 



.TO LOCAL 

 OFFICES 



TRUNK 



BLOCK 



CONNECTOR 



FOREIGN 



AREA 



TRANSLATOR 



CONNECTOR 



FOREIGN 

 TRANSLATOR 



Fig. 1 — Schematic diagram of crossbar switching system for CSP's. 



