Drawing illustrating Tesla’s unipolar vacuum tube

Figure 2. Drawing illustrates Tesla’s unipolar vacuum tube, consisting of a glass bulb (b), a single electrode (e), and a lead-in conductor (c).The tube can be adapted for use with two electrodes by placing the second electrode at the levels indicated by the dotted lines. Published in Electrical Review, New York, April 1, 1896. (Reprinted from reference 3.)