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BELL SYSTEM TECHNICAL JOURNAL 



which gives service Y db poorer has a loss of F db more than the loss 

 of the reference loop. Receiving loops are rated relative to the refer- 

 ence receiving loop in the same way, the difference in effective loss 

 of the two conditions being subtracted from or added to the assigned 

 effective loss of the reference receiving loop. These losses are given 

 in curve form, similar to Fig. 3. They include the effects of variation 



I 2 3 4 5 6 7 8 9 10 II 12 13 14 



LOOP LOSS IN DECIBELS 



Fig. 3 — Effective loop losses. 



in sidetone and distortion with loop length as well as the variation 

 in volume loss. In some cases the loss on extremely short loops is 

 greater than on loops of intermediate length because of the rapid 

 increase in sidetone with decrease in loop length. 



The effective loss due to substituting any type of trunk for the 

 reference trunk in the reference system could be determined and the 

 loss data for various lengths presented in curve form in the same way 

 that effective loop losses are presented, but the same curve would not 

 apply for the loss of this type of trunk between other than the refer- 

 ence loops. If two or more such curves, as shown in Fig. 4, are deter- 

 mined for a particular type of trunk when used with different loops, 



