. American telephone practice . FIG. OBSTACLES. is good practice to allow about one inch air space between the outercourse of brick and the inner in order to render the interior as dryas possible. A common-sized manhole is five by five by five feet, and smaller sizes down to three bv three feet with five feet head room are 844 AMERICAN TELEPHONE PRACTICE. also common. As a rule a manhole should provide at least enoughroom for two men to work in conveniently. Of course, where agreat number of ducts enter a manhole the size must be increasedaccordingly. After the conduits are laid
. American telephone practice . FIG. OBSTACLES. is good practice to allow about one inch air space between the outercourse of brick and the inner in order to render the interior as dryas possible. A common-sized manhole is five by five by five feet, and smaller sizes down to three bv three feet with five feet head room are 844 AMERICAN TELEPHONE PRACTICE. also common. As a rule a manhole should provide at least enoughroom for two men to work in conveniently. Of course, where agreat number of ducts enter a manhole the size must be increasedaccordingly. After the conduits are laid and the manholes finished the nextstep is the drawing in of the cables. In order to accomplish thisa process called rodding is in most cases first necessary, in orderthat a rope may be stretched through the duct, which is afterwardsto be used for drawing in the cable itself. For this purpose a largenumber of wooden rods about three-fourths of an inch in diameterand four feet long, and equipped with screw or bayonet joints ateac
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