Issue 17 and Volume 52.

UNDERGROUND CABLE FOR FIRE TELEGRAPH SERVICE. In these days when municipalities require operating companies to put their conductors underground, It follows that the municipalities themselves should do their share, and likewise put their own wires under ground. Reduction in maintenance and depreciation, and increased reliability (all to he expected in a properly designed and installed system) makes such cables a very good investment. The essentials in any underground cable are: (1) The conductor; (2) the insulation; (3) the sheath. For the conductor, copper has been used exclusively for ordinary service. This is due to the fact up to the time of the introduction of aluminum for use as electrical conductors a given conductivity as expressed in resistance per thousand feet of the given size of the wire could he attained most cheaply by the use of copper, notwithstanding the fact that some metals (silver, for instance) actually had a higher…

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