Vacuum tube diode

The device is a glass bulb containing structures. The bulb has all the air evacuated (the vacuum). The internal structures are a filament that has a current going through it and used to heat the nearby emitter, which gives off electrons when heated. The other structure is the collector which, when it has a positive voltage will collect the electrons, and when it has a negative voltage will not. These structures are connected to the outside of the bulb with wires. So there is a possibility of an electron current passing through this device, and this current depends on the voltage between the emitter and the collector. That is the diode part.