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BELL SYSTEM TECHNICAL JOURNAL 



mechanical requirements, etc., it has often been found useful to com- 

 pute sub-rates with respect to such classifications of trouble. A 

 typical sub-rate is indicated by the fine dotted line of Fig. 9. Ex- 



Fig. 9 — Rates showing the quality of similar product supplied by three independent 



companies 



perience has also shown the practicability of rating the quality of out- 

 put of the individual operators and gangs in some classes of work for 

 the purpose of comparing workmanship. 



The principal advantage of these latter steps is to provide a ready 

 means for tracing causes of trouble. 



