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BELL SYSTEM TECHNICAL JOURNAL 



cannot be dealt with on the basis of averages alone but must include 

 some measure of their range, such, for example, as the standard 

 deviation/ The available data indicate that average transmitter 

 resistances and standard deviations which lie within the area bounded 

 by the dotted curve. Fig. 5, will have no adverse effect on circuit 



5 10 15 20 25 30 35 40 45 50 55 60 



STANDARD DEVIATION IN OHMS 



Fig. 5 — Limiting values of transmitter resistance. 



operation in the Bell System plant. This curve is based on certain 

 marginal circuits of which there are a number in everyday use. An 

 important transmitter resistance in determining the performance of 

 associated apparatus in these circuits is the resistance during the 

 period when the call is being established. This resistance is referred 



