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BELL SYSTEM TECHNICAL JOURNAL 



in the purifying process, will be practically nullified by the acetate 

 treatment. 



An interesting example of how cellulose acetate treatment improves 

 the electrical balance of a circuit is given in Fig. 10, which shows the 

 capacitance unbalances between phantom and side circuits in a four- 

 conductor wire for toll use. The capacitance unbalance is the main 

 cause of electrical interference between the two circuits mentioned 

 above and it is desirable to have this value as low as possible. Al- 

 though there are some differences in design in these two types of wire, 

 practically all the improvement is due to the acetate insulation. 



95 



U 

 > > 



P b 85 

 < O 



a 3 75 

 65 



5 6 7 8 



TIME IN DAYS 



Pig 10 — A-C. capacitance unbalance between the phantom and side circuits of 50 

 feet of quadded 22-gauge wire. 



Application to Apparatus 

 Advantages in the use of cellulose acetate treated insulation are 

 derived from several sources of which the most important is the im- 

 provement in electrical characteristics of cotton and silk, as illustrated 

 by the foregoing graphs. For example, this improvement is sufficient 

 in many cases to permit the substitution of cotton for silk, with a 

 resulting substantial reduction in cost. In other cases, silk has been 

 retained and a cable of much higher quality has been made available 



