Ballard, William Cyrus, Jr · New York [etc.] McGraw-Hill company, inc. · leaf 18
permanent magnets,electro magnets. Fig. 2.—Telephone transmitter or microphone and telephone receiverremoved from their cases to show internal construction. this allows the battery to send a comparatively large currentthrough the circuit. When pressure is removed the resistance 4 ELEMENTS OF RADIO…
Radio
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![An illustration from Telephones and telegraphs: 1902 : [and Municipal electric fire alarm and police patrol systems] (1906)](https://img.insideoutlibrary.com/img/200/ia-cu31924022817674-54-12.webp)
