106 BELL SYSTEM TECHNICAL JOURNAL 



4. The control circuit will signal to the terminating sender the 

 number of the incoming link frame in which the incoming trunk 

 appears. This frame identification will be used later in establishing 

 the connection to the called line. 



5. The control circuit will then disconnect after checking to insure 

 that the connection to the sender has been properly established and 

 that it will be held under control of the trunk and sender circuits after 

 the control circuit leaves the connection. 



As soon as this operation has been completed, which takes but a 

 fraction of a second, the terminating sender will be in direct connection 

 with the subscriber sender in the originating end of the connection. 

 This path may be traced, by referring to Fig. 13, from the subscriber 

 sender through the sender link frame, through the district junctor, 

 through the district link and office link frames, over the outgoing 

 trunk to the incoming trunk, and through the terminating sender link 

 frame to the terminating sender. 



At this stage of the connection the calling subscriber is still con- 

 nected with the subscriber sender, and dialing may be still in progress. 

 As the subscriber proceeds with the dialing of the digits of the called 

 number, the subscriber sender will transfer them to the terminating 

 sender. This is done by means of impulses transmitted over the 

 circuit paths between the two senders. When the subscriber sender 

 has completed the transfer of the called number to the terminating 

 sender, the subscriber sender will be released and the calling line 

 will then be connected through the district junctor to the incoming 

 trunk. 



When the terminating sender has secured the record of the called 

 line number, the sender then connects to an idle terminating marker 

 by means of multi-contact relays of a connector circuit. 



The next stage in the progress of the call is shown in Fig. 14. The 

 terminating marker is the principal control unit at this point in the 

 connection. Its principal function is to provide means for establishing 

 the connection from the incoming trunk to the called subscriber line. 



When the terminating sender has connected to the terminating 

 marker, the sender will transfer both the called line number and the 

 incoming link frame identification to the marker. The terminating 

 marker then proceeds to establish the connection to the called line as 

 follows : 



1. It connects itself to the particular "number group connector" 

 circuit including the "block relay" frame in which the called line 

 appears in its numerical sequence. All subscriber lines are provided 

 with a set of three test terminals which appear on the block relay 



