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Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems (1921)

Smith, Arthur Bessey, b. 1875, Campbell, Wilson Lee · New York : McGraw-Hill · leaf 258

An illustration from Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems, 1921, leaf 258 — Key Springs Hartied jX fo ma He before 50w> Req.CD. I I Reserve \_i Comm.toPos.. I-fal switchboard of the Dean Electi

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