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BELL SYSTEM TECHNICAL JOURNAL 



curve were obtained by averaging, for each five-degree range of tem- 

 perature, the insulation resistances obtained by measurements made 



??600 



Fig. 1 — Variation of insulation resistance with electrification period — -typical 50 mile 



aerial cable pair. 



E400 



10 20 30 40 bO 60 70 80 90 



Outside Temperature at Measuring Station -Degrees Fatirentieit 



Fig. 2 — Variation of average insulation resistance with temperature — typical repeater 



section of aerial cable. 



daily over the course of a year on representative pairs in a repeater 

 section, using electrification periods one minute long. It has been found 

 that the percentage change in insulation resistance per degree change in 



