File:The practical telephone handbook and guide to the telephonic exchange (1906) (14569529240).jpg

Identifier: practicaltelepho00pool (find matches)
Title: The practical telephone handbook and guide to the telephonic exchange
Year: 1906 (1900s)
Authors: Poole, Joseph
Subjects: Telephone
Publisher: New York, Macmillan Co.
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Boston Library Consortium Member Libraries

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Text Appearing Before Image:
Fig. 380.—3-Duct Concrete-Block Conduit then be well covered with cement. A strip of canvas coatedwith asphalt is passed right round the joint under the blocksto close up the space, and the recesses left for this purpose are 384 PRACTICAL TELEPHONE HANDBOOK afterwards closed up with cement, as shown in Fig. 381. Toensure that the ducts are properly in line, a lead mandril 4feet long and 2; inches is passed through. The ends of unused ducts should be kept plugged up. -/ S^
Text Appearing After Image:
—loeorer Fig. 381.—Method of making Joint in Concrete-Block Conduits When stored, the concrete blocks should be kept moist, asthey are apt to crumble away when left dry. Glazed Earthenware Ducts.—These have been used veryextensively in the London district by the British Post Officeauthorities. Fig. 382 shows half an end view and half a sectionof one of the pipes, which are single ducts having a 3 J-inch bore,with the ends well rounded. They aremade of an octagonal outside section,and in two lengths of 18 inches and 24inches, the latter one being only usedfor connecting the ducts into the man-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 enveloped in mortar cement,and to prevent the mortar getting into the pipes the joints areclosely c

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