1060 



Voltaic Electricity. Section 11: Telephony and Microphony. 



No. 63 lOO- 



eS 400. 1 : 7. 



63402. 2:5. 



63 403. 1 : 2. 



63407. 



s. d. 



0.0 



63.400. Photophonic Apparatus for Acetylene Light, for showing the sensitivity of Selenium 

 to Light, Figure, mounted on board, with manometric capsule, sound horn, pointed 

 burner, highly sensitive Selenium cell and reflector, switch and terminals; including 

 Acetylene Generator but not battery or telephone 6. 



The apparatus is constructed in a like manner to No. 63,398, the only difference being that a 

 Selenium cell and a spherical reflector take the place of the parabolic reflector. To complete the 

 apparatus there should be a source of current (see remark to No. 63,397) and a telephone No. 63,370. 

 Battery and Telephone are put in series with the Selenium Cell. It can be shewn that the transmission 

 of the sound waves only results from the fluctuations in light by the fact that transmission ceases 

 when an opaque body is held between acetylene flame and Selenium Cell. 



63.401. - - idem, with a Parabolic Reflector, which can be fitted instead of the Selenium 

 Cell so as to be able to use the apparatus as a photophonic transmitting station also, 



in accordance with Fig. 63,398 6. 10. 



Selenium Cells. 



63.402. Selenium Cell, flat rectangular shape, in wood box, Figure, from 20,000 to 

 80,000 ohms resistance. The ratio of resistances in brightly lighted and darkened state 

 is at least 1 : 10 



Selenium Cells, round pattern, with metal slide, Figure: 



List No. 63 

 Diameter of Aperture mm 25 



1.16.0 



63,406. Stand with joint, for Nos. 63,40263,405 



1.16.0 



