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inside diameter which is the maximum size of sheath which has been 

 found generally economical in telephone plants in this country. By 

 1912 further improvements in manufacturing equipment made it pos- 

 sible to use insulating paper of even smaller dimensions and to get 909 

 pairs of wire into the same diameter of sheath. 



Fig. 4 — Pulling core into lead pipe, method used prior to 1894 



On account of increased congestion in the densely populated sections 

 of the larger cities, there was continued demand for more pairs of wire 

 per cable, and in 1914 the first 1,212-pair 24 A.W. gauge cables were 

 produced. This 24-gauge wire was insulated with paper Vie in. wide 

 and 23/2 mils thick. The mutual capacitance between the two wires of 

 a pair in this cable averages about .079 microfarad per mile, which 

 allows a normal margin below the guaranteed value shown in Table 1. 



TABLE 1 



