CROSSBAR TANDEM AS A TOLL SWITCHING SYSTEM 



103 



and that the marker has mformed the sender the called number is to be 

 sent as received. The outpulsing control circuit is connected to each 

 register in turn through the steering circuit SI, S2, etc. and sends the 

 digits stored. 



Case 2 illustrates a situation where the sender has stored ten digits 

 in registers 1 to 10 and received information from the marker to delete 

 the digits in registers 1 to 3 inclusive and to substitute the arbitrary 

 digits stored in registers AA, AB and AC. The outpulsing circuit is 

 first connected to register AA through steering circuit PSl, then to AB 

 through PS2, continuing in a left to right sequence until all digits are 

 outpulsed. 



Case 3 covers a condition where the sender has stored seven digits and 

 has obtained information from the marker to prefix the two digits 

 stored in registers AB and AC. Outpulsing begins at the AB register 

 through steering circuit PS2 and then advances through steering circuit 

 PS3 to the AC register, continuing in a left to right seciuence until all 

 digits have been transmitted. 



These are only a few of the many combinations that are used to give 

 the crossbar tandem control switching equipment complete pulsing 

 flexibility. 



SIX-DIGIT TRANSLATION 



Six-digit translation will be another feature added to the crossbar 

 tandem system. When only three digits are translated, it is necessary to 

 direct all calls to a foreign area over a single route. The ability to trans- 

 late six digits permits the establishment of two or more routes from the 

 switching center to or towards the foreign area. This is shown in Fig. 



LOCAL 

 OFFICE 



NUMBER OUTPULSED 

 04-MA2-1234 



MADISON 

 OFFICE 



MA2-I234 



MADISON 2- 



1234 



STEP-BY-STEP 

 PRIMARY CENTER 



Fig. 8 — Prefixing. 



