250 



BELL SYSTEM TECHNICAL JOURNAL 



salt solution in the bottom of the tank and constant temperature 

 within very narrow limits is maintained in the tank by placing the 

 entire assembly inside a cabinet or oven automatically controlled to 

 ± 0.5 degrees Fahrenheit. Due to the heat insulation it has been 



50 



60 65 70 75 80 86 



PERCENT RELATIVE HUMIDITY 



90 



Fig. 5 — Transmission loss in 50 ft. of twisted pair wire insulated with double servings 



of equal thickness. 



found that temperature variations within the tank are reduced to the 

 vanishing point for all practical purposes. 



This is very important as it has been found that fluctuations in the 

 temperature of the test chamber introduce large errors in the insulation 



