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BELL SYSTEM TECHNICAL JOURNAL 



breakdown. This method of reducing spark delay time was not practical, 

 however, and other means were sought. A solution was found through a 

 rediscovery of the efficacy of corona prior to breakdown which came about 

 through the introduction of a properly placed sharp edge on the cathode. 

 Although this edge was apart from the sparking area of the cathode, 100% 

 breakdown of the gaps was obtained and spark delay time so reduced 



Fig. 2 — Experimental model of rotary gap showing corona points. 



that mechanical limitations alone controlled the variation in time of 

 breakdown. 



The essential features of the gap as finally developed for this project are 

 shown in the photograph of an experimental model, Fig. 2, and in the per- 

 spective drawing and accompanying diagram. Fig. 3. The electrodes are of 

 tungsten as in the earlier design, and corona points are introduced by the 

 addition of the rods holding sharp metal points mounted on the same metal 



