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BELL SYSTEM TECHNICAL JOURNAL 



As soon as the called line is reached, the sender is dropped from the 

 circuit to be available for another connection. It is not held during 

 the period of ringing, during the time that the busy signal is being 

 given, if the line is busy, or during any part of the period of con- 

 versation. 



It will be noted that the method of selection is not on a decimal 

 basis. The first selection is to choose one of five brushes on the in- 

 coming selector as already explained ; that is, we choose that partucular 

 fifth of the terminals in which the called line happens to be, and since 

 1-5 of 10,000 is 2000, we choose the 2000 group desired. The next 

 selection is by groups of 500, which is again non-decimal. This 

 " translation," as it is called, of the number from the decimal notation, 

 as dialed by the subscriber, into the notation as needed by the selectors, 

 is taken care of very simply in the senders. 



Calls from Machine Switching to Manual Offices. Calls from ma- 

 chine switching to manual offices are handled at the manual office on 

 call indicator "B" positions. Fig. 21 shows a diagram of the equip- 

 ment used to connect such a call to a subscriber in the manual office. 



TRUNK. 

 POSITION- 



CALLED SUBSCRIBER 



TO OFFICE 



FRAME_ 

 M.S. I 



OFFICE 



TRUNIN 

 RELAYS 



Fig. 21 — Diagram of Connection from Machine Switching to Manual 



The call progresses through the district and office selector in the 

 same manner as described for the machine switching call, but the 

 trunk which it takes up leads to a call indicator "B" position in the 

 manual office selected. The operator is notified that a call has reached 

 her position by the lighting of a lamp associated with the cord and 

 plug in which the incoming trunk terminates. Upon perceiving this 

 signal, she presses a display key associated with that trunk, and 

 thereupon the called subscriber's number is displayed on a bank 



