Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book (1902)
Swoope, Coates Walton. [from old catalog] · New York, D. Van Nostrand company · leaf 347
Fig. 297.—Connections of a Telephone System for Two Stations.Blake microphones are used as transmitters and Bell telephones as receivers. telephone, become materially weakened when they have toflow over lines of considerable length and resistance, so thatthe sounds in many cases become inaudible.…
Electricity · Magnetism
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