A tube has its cathode connected to the common ground line. The grid connects to one end of a resistor. The other end of the resistor connects to the negative end of a battery. The positive end is grounded. The grid also connects to one end of a capacitor and the other end connects to a terminal point which is indicated as having a sine wave applied to it. There is a zero center voltmeter connected from the grid to ground. The plate of the tube connects through a resistor to B plus. There is another identical voltmeter connected from the plate to ground. The voltmeter in the grid circuit is indicating a negative voltage. The plate voltmeter is indicating a positive voltage. Between the cathode and grid is the space charge represented by a large number of dots moving around randomly. There a few electrons passing through the grid and on to the plate. As time progresses the grid meter goes less negative. The number of electrons getting through the grid increases and the plate meter indicates a lower voltage. Neither meter gets all the way to zero. Both meters move farther away from zero and the number of electrons getting through to the plate decreases. The electron stream is never cut completely off. End of verbal description.