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BELL SYSTEM TECHNICAL JOURNAL 



This would be roughly where Sf ^ — 2 db. The percentage of cable 

 section return losses which would exceed this value, however, would 

 be about 80 per cent, so a line which gave such a low singing margin 

 would, in general, tend to be made up of a few very low-return losses 



10 20 30 40 50 60 70 80 90 100 



PER CENT OF CASES LESS THAN INDICATED VALUE 



Fig. 7 — Return loss distributions of cable pairs (Sf), equipment (Se), and the 



combination (5c). 



and a considerable percentage of higher-return losses. It, therefore, 

 seems that this value of cable-return loss, if combined with the equip- 

 ment and terminating return loss, would not be sufficiently degraded 

 to consider that degradation as a fair average degradation for the 

 entire curve. On the other hand, if the cable return loss which is 



