. On the left the V sub BB, not labeled here, connects through a resistor, then another resistor to the base rectangle. The junction of the two resistors connects to a representation of a voltmeter with zero at the center of its scale, negative on the left and positive on the right. Also connected to the two resistors is a capacitor with its other end going to a connection point. A sine wave is indicated as being applied to the connection point. On the right the collector connects through a resistor to V sub CC and another similar voltmeter is connected to the collector. The negative leads of both meters are connected to the common line. In the emitter rectangle dots representing electrons are moving around randomly while also moving upward. In the base rectangle circles representing holes are dancing around but showing no movement in any direction. The electrons are moving upward through the base and on into the collector rectangle. Occasionally an electron will disappear while in the base region due to recombination but the vast majority of them make it across the base. Once in the collector rectangle they continue on to the top line where they are absorbed by the battery. The voltmeter on the left is indicating the amount of voltage at the junction of the two resistors and so, indirectly, the base current. As the voltmeter swings to the right the number of electrons leaving the emitter and crossing the base increases. As the meter swings to the left, closer to zero, the number of electrons crossing the base decreases to just a few. The voltmeter on the right is also swinging from near zero to positive maximum but it is moving opposite to the meter on the left. That is when the meter on the left goes up the one on the right goes down and vice versa.
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