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BELL SYSTEM TECHNICAL JOURNAL 



ler voltage is made to approach the given voltage. Consider the case illus- 

 trated in Fig. 19. The arrows indicate the direction of repeller voltage vari- 

 ation. If we start from the middle of the characteristic and move toward 

 more negative values of repeller voltage, the amplitude of oscillation varies 

 continuously until a critical value is reached, at which a sudden decrease in 



NEGATIVE REPELLER VOLTAGE »- 



Fig. 19.— A possible variation of power and frequency with repeller voltage when there 

 is electronic hysteresis. The arrows indicate the direction of variation of repeller voltage. 



amplitude is observed. This drop may be to zero amplitude as shown or to a 

 finite amplitude. In the latter case the amplitude may again decrease con- 

 tinuously as the repeller voltage is continuously varied to a new critical 

 value, where a second drop occurs, etc. until finally the output falls to zero. 

 In every observed case, even for more than one drop, the oscillation always 

 dropped to zero discontinuously. Upon retracing the repeller voltage varia- 

 tion, oscillation does not restart at the repeller voltage at which it stopped 

 but remains zero until a less negative value is reached, at which point the 



