352 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



matching function by gaining access to a set of line links, a set of trunk 

 links and a set of junctors on the basis of its knowledge of line and trunk 

 location. It tests for three idle elements of like number within these sets 

 and picks the lowest numbered idle channel available for making the 

 connection. If it is impossible to match three idle elements and there is 

 more than one set of junctors between frames, the marker will change the 

 junctors and make a second attempt at matching. This marker function 

 is performed by a six-stage allotting circuit which advances one step 

 for every match operation. Depending upon the number of junctor 

 subgroups, the allotter is arranged to rotate the first choice subgroup 

 on each subsequent match operation and provide an alternate sub- 

 group if the first match attempt fails. This system tends to equalize the 

 use of junctors. 



For use by the match operator, a channel card for each set of ten links 

 or junctors is provided. Each card, as shown on Fig. 25, has ten pockets, 

 one per link or junctor element, in which can be inserted a busy tab. 

 When the three cards required for a particular connection are identified, 

 they can be stacked as shown on Fig. 26 (note the difference in card 

 size) and the idle channels are immediately obvious. In this case, channel 

 5 is the lowest available one and would be assigned to the call. 



The identity of each card corresponding to a set of links or junctors 



Fig. 26 — Channel matching procedure. 



