CHAPTER V

APPLICATIONS OF SELENIUM CELLS 51 Photometric Applications. Transmission of Speech Over Beams of Light. Automatic Control of Light Buoys and Isolated Lights. As Recorder of Sunlight. Astronomical Applications. Talking Pictures. The Phonoptican, How the Blind May Read by Sound. Controlling Mechanisms at a Distance. Electric Dog. Use in Cable Telegraphy. Burglar Alarm. Selenium Batteries, Current Generators. Telephonic Properties. Effect of Different Current Sources on Sensitiveness of Cells.