The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 413
an-holes. Laying.—A foundation is first madeby laying a bed of concrete at thebottom of the excavated trench, thisbed being stiffened and strengthenedby lengths of T section iron embedded in the concrete. The 18-inch lengths of ducts are then laid over the founda-tion end to end, and completely… … Fig. 382.—GlazedEarthenware Duct UNDERGROUND WORK 3B5 over both the concrete and cast-iron conduits, as the shortlengths used allow of slight curves being negotiated to avoidvarious obstructions met with. It has also the advantage overconcrete conduits of being practically gas and water proof.It…
Telephone
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