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BELL SYSTEM TECHNICAL JOURNAL 



and other methods and apparatus which are the result of recent 

 developments. Lead-covered aerial cable supported on wooden pole 

 lines is to be used in general on all of the routes except in the two 

 sections just mentioned and through cities or where special condi- 

 tions exist for short distances. The possibility of now using con- 

 ductors of No. 16 and No. 19 A. W. G. instead of conductors up to 



Fig. 5 — General View of Pole Line Carrying Aerial Cable 



No. 10 A. W. G. as in the older cables, has contributed to make aerial 

 construction rather than underground conduit the more economical 

 in many sections, as one cable will provide for a much greater number 

 of circuits and consequently fewer cables will be required. 



Line Construction 



The general type of aerial construction which was used for over 

 250 miles of the total distance of 302 miles from Philadelphia to Pitts- 

 burgh may be seen from Figs. 5 and 6 which illustrate the poles, steel 

 suspension strand, metal supporting rings and the cable. The poles 

 are 25-foot untreated chestnut spaced 100 feet apart and designed 

 to carry additional cables in the future. While the poles are new 

 and carry only one cable they have a factor of safety of about 9 under 

 the most severe storm conditions expected, but this will, of course, be 

 reduced as other cables are placed and will gradually be decreased 

 on account of decay at the ground line until it becomes necessary to 

 start replacing the poles. Many of these poles were grown near the 

 locations where they now stand. In other sections, it is planned 



