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The practical telephone handbook and guide to the telephonic exchange (1906)

Poole, Joseph · New York, Macmillan Co. · leaf 413

An illustration from The practical telephone handbook and guide to the telephonic exchange, 1906, leaf 413 — 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… … —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.…

Telephone

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