Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc. (1916)
American Technical Society · Chicago : American Technical Society · leaf 212
rce of light S. The resistance of the selenium cellwas approximately 1,200 ohms in darkness, and about half thatwhen fully illuminated. The mode of speech-transmission is sosimilar to that of the radiophone that further description is notnecessary. The photophone, as proposed by Bell, may be made… … T/^Nsrr/rrc/f V\z. 2. Bells Photophone of the device for distances relatively long necessitated the use ofpowerful sources of light and adequate means for controlling thesame, the invention remained but a beautiful laboratory experimentuntil the discovery of the speaking arc by Simon in 1897 opened…
Electrical engineering
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