REMOTE CONTROLLED LINE CONCENTRATOR 



257 



5. SWITCHING PLAN 



The plan for serving lines directly terminating in a No. 5 Crossbar office 

 is shown in Fig. 5(a). Each line has access through a primary line switch 

 to 10 line links. The line links couple the primary and secondary switches 

 together so that each line has access to all of the 100 junctors to the trunk 

 link switching stage. Each primary line switch group accommodates 

 from 19 to 59 lines (one line terminal being reserved for no-test calls). 

 A line link frame contains 10 groups of primary line switches.^* 

 . The remote concentrator plan merely extends these line links as trunks 

 to the remote location. However, an extra crossbar switching stage is 

 introduced in the central office to connect the links to the secondary line 

 switches with the concentrator trunks as shown in Fig. 5(b). Since each 

 line does not have full access to the trunks, the path chosen by the marker 

 to complete calls through the trunk link frame may then be independent 

 of the selection of a concentrator trunk with access to the line. This 

 arrangement minimizes call blocking, simplifies the selection of a matched 

 path by the marker, and the additional crossbar switch hold magnet 

 serves also as a supervisory relay to initiate the transmission of disconnect 

 signals over the trunk. 



In addition to the 10 concentrator trunks used for talking paths, 2 

 additional cable pairs are provided from each concentrator to the central 

 office for signaling and power supply purposes. The use of these two pairs 

 of control conductors is described in detail in Section 6g. 



The concentrator acts as a slave unit under complete control of the 

 central office. The line busy and service request signals originate at the 



LINE 



60 LINES 



I 



1 2 3 



5 6 



8 9 10 11 



Fig 4. — Concentrator trunk 

 to line crosspoint pattern and 

 preference order 



CONCENTRATOR 

 TRUNKS 



1 



5 6 



8 



VERTICAL GROUPS OF FIVE LINES EACH " 



ORDER OF PREFERENCE 



GAS TUBE REED -RELAY 

 CROSS POINTS 



10 11 



