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BELL SYSTEM TECHNICAL JOURNAL 



tunity for their mutual use by the calls from either subgroup. In this 

 particular case, however, the hunt or access has been increased from 

 10 to 15 terminals. If we wish to retain the operation of the system 

 on 10-point switching equipment we must compress the trunks into 

 some such form as indicated in Fig. 6(C). In so doing we have very 

 likely increased the split group efficiency of the trunks but, at the same 

 time, on account of their fewer total number the load originally sub- 

 mitted may not be adequately served. Hence, a remedy such as shown 

 in Fig. 6{D) may perhaps be devised: that is, the addition of more sub- 

 groups of the restricted-availability trunks. The study of the actual 

 carrying capacities of these various arrangements is reserved for a 

 later point in this paper. 



In general, then, we may represent any such plan of trunking by 

 the schematics of Hgs. 7 (A) and 7{B). These are called "simple 



COMMON 



'trunks 



INDIVIDUAL 

 TRUNKS 



ai 



32 



33 



34 



Fig. 7 (A) — Simple graded multiple with g subgroups. 



ai 



62 



^3 



84 



as 



36 



Fig. 7{B) — -Example of a non-symmetrical progressive graded multiple. 



graded multiples" and "progressive graded multiples," respectively, 

 and by varying the number and placement of the trunks composing 

 them a very large variety of arrangements indeed may be obtained. 

 Here all calls hunt from the "bottom" of the group over a particular 



