1. 
   Phototube
   A phototube is a type of gas-filled or vacuum tube that is extremely sensitive to light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum. ==Operating principles== Phototubes operate according to the photoelectric effect: Incoming photons strike a photocathode, g...
   Found op http://en.wikipedia.org/wiki/Phototube
   
   
2. 
   phototube
   a photosensitive tube in which the photoemissive effect is utilized
   Found op http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=531-34-02
   
   

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