I think ??? when the grid is fired positive it allows electrons to flow from the neg charged cathode to the pos charged plate. There were triodes and pentodes and that's all I can remember. I seem to recall, as the grid went pos with a sine wave, the plate followed negatively, but with an amplified wave.??? Time for another little brown pill.Rock: Your post #20 brings back many memories, NATTC Memphis AFU-A School65-66. Tube theory, had 2 1st class ET's (maybe, probably bosun's mates) trying to teach one particular type tube, all I can remember is them saying (and repeating) "AFTER the tube has fired this is what happens". Everybody asked "How does it fire?", and they repeated "AFTER the tube has fired this is what happens".
Paul in CT