Part 4/7:
In circuit diagrams, vacuum tubes are typically represented with symbols indicating their internal parts: the heater, the grid, and the plate. In a typical setup with three valves (or tubes), each symbol highlights these elements, showing how they interact within the circuit.
The internal operation can be summarized as follows:
The heater produces electrons.
The grid modulates the electron flow by varying its voltage.
The plate collects the electrons, producing an output current.