Electronic: Switching circuits

We read with much interest the article in the May 1938 issue of Electrical Engineering entitled “Some Electronic Switching Circuits,” by C. C. Shumard. We should like very much to discuss one feature of this paper. We developed an impulse-voltage generator somewhat similar in principle to that described in figure 6 of Mr. Shumard´s article. We arranged the circuit as indicated in figure 1 of this letter. By supporting the type-34 linearity tube on porcelain insulators, together with its filament and screen-biasing batteries, we were able to reduce the capacitance until we could get a voltage impulse lasting one microsecond. We were not able to reduce the time of the impulse below this minimum figure. Mr. Shumard states that with the assumed values of resistance and capacitance the minimum impulse interval should be &1/4; microsecond. We attempted to use a circuit like that described in figure 6a of his article, but found that the capacitance between ground and the anode side of the type-885 tube was too great to obtain the impulse duration mentioned. We should like very much to know if Mr. Shumard was successful in obtaining an impulse of &1/4; microfarad duration. If he obtained this low time interval, we should like to know what special provisions, if any, he made in the design of the sweep circuit.