The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 412
ND WORK 3*3 crete bearers firmly bedded in the earth. Fig. 380 showsa 3-duct block complete. Laying.—The blocks are laid so as to leave a space of fths of Groove for Iron Jointing Rods. OOQOOOOOO Ducts,3 1-16 diameter. Groove forIron Joiuting Rods. ^ _ __/_^£ y Fig. 379.—End view of 9-Duct Concrete… … 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…
Telephone
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