1. underground electric subway
A subway for the enclosing of electric telegraph and other conductors under the surface, generally in the line of streets, to do away with telegraph poles and aerial lines of wire. Many systems have been devised. The general type includes tubes called ducts in sets, called conduits, bedded in concrete or otherwise protected. Every two or three hundred feet the sets lead into a cistern-like cavity called a manhole. The insulated wires or cables, generally sheathed with a lead alloy are introduced into the tubes through the man-holes. A rope is first fed through the tube. To do this short rods which screw together are generally employed. One by one they are introduced, and each end one is screwed to the series of rods already in the duct. When the end of the duct is reached the rope is fastened to the last rod, and the rods are then drawn through, unscrewed one by one and removed, the rope following them. By means of the rope a windlass or capstan may be applied to draw the cable into the duct. At least at every second man-hole the cables have to be spliced.
Each cable may contain a large number of conductors of small size for telephoning, or a smaller number for electric light and power. The tendency is now to separate the different classes of wires in important lines, placing the heavier wires on one side of the street and the telephone and telegraph wires on the other. This of course necessitates two separate conduits.
The advantage of underground distribution affects not only the appearance of streets in doing away with unsightly telegraph poles, but it also removes an element of danger at fires. Aerial wires interfere greatly with the handling of ladders at fires, and expose the firemen who attempt to cut them to danger to their lives from shock.
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Definitions of underground electric subway
