. Electronic apparatus for biological research . Figure screen current, as in normal pentode usage. If now a negative trigger pulse be apphed to the suppressor the anode current is reduced and electrons flow instead to the screen, increasing the screen current and reducing the screen potential. This reduction is transferred via C to the suppressor, producing a further fall in anode current and increase in screen current. Cumulative action then occurs as a result of which all the cathode current goes to the screen and the anode current is cut off. This state of affairs persists until, as a
. Electronic apparatus for biological research . Figure screen current, as in normal pentode usage. If now a negative trigger pulse be apphed to the suppressor the anode current is reduced and electrons flow instead to the screen, increasing the screen current and reducing the screen potential. This reduction is transferred via C to the suppressor, producing a further fall in anode current and increase in screen current. Cumulative action then occurs as a result of which all the cathode current goes to the screen and the anode current is cut off. This state of affairs persists until, as a result of re-adjustment of the charge on C, the suppressor potential returns exponentially to a point at which anode current once more begins to flow. The screen current then falls, the screen potential rises and a reverse cumulative action occurs. The waveforms are similar to Figure , except that screen potential should replace V-^ anode potential, and suppressor potential the V^ grid potential. Uses for single square waves—^The pulses produced by the flip-flop and transitron may be used for applications where their shape is specifically applicable, as in square wave stimulation, or use may primarily be made of the duration of the wave for the production of delays. If the square wave is passed through a CR network of short time constant*, then a pip is generated at the beginning and end of the wave, and the second pip selected by an appropriately connected diode, as in Figure The second pip is then used to trigger further circuits. Flip-flop circuits are so commonplace that there is little point in trying to refer the reader to all possible uses for them. The triggered transitron is * Sometimes called a 'differentiating' circuit, since the output is responsive to rates of change at the input, rather than to the input itself. 237
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