POLYETHYLENE INSULATED TELEPHONE CABLE 



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on concurrently with that of solid polyethylene. In expanded polyethylene 

 insulation the cost, as would be expected, varies with the degree of ex- 

 pansion. There are two reasons for this: first, as the proportion of gas 

 is increased, less polyethylene is used in the insulation, and second, be- 

 cause of the lower dielectric constant, the cable can be made smaller 

 for the same attenuation, resulting in savings in sheathing materials. 

 An initial trial installation of about nineteen miles of 51 -pair 19-gauge 

 expanded polyethylene insulated cable has been completed between 

 Grandville and Zeeland, Michigan. This route is to be developed for N 

 carrier, and since recent Systems' studies have indicated the lower over- 

 all costs will result if low attenuation cable is used, the Grandville- 

 Zeeland cable was designed for a capacitance of 0.066 microfarad per 

 mile rather than the 0.084 microfarad per mile capacitance for which 

 earlier polyethylene-insulated cables were designed. The Cooperstown, 

 Trout Lake and Grandville cables are illustrated in Fig. 5. 



It is of interest to compare polyethylene-insulated cables with paper- 

 insulated cables having the same voice frequency attenuation. Some of 

 the more important characteristics are shown in Table II. It will be 



Fig. 4— Installation of Cooperstown-Cherry Valley (N. Y.) cable. 



