1. Tetrode: A tetrode is a four-electrode device used to amplify signals and operate in power modes. It is used in circuits like an amplifier, oscillator, and modulator.
2. Heater Element: A heater element is a device that generates heat and helps in maintaining the temperature and desired temperature inside a tube.
3. Anode: The anode is the positive electrode of a vacuum tube and it is the terminal that is connected to the positive power supply. It is usually found in the center of the tube and moved around a magnet to create a magnetic field.
4. Cathode: The cathode is the negative electrode in a vacuum tube. It is the terminal that is connected to the negative power supply and is also found in the center of the tube.
5. Grid: A grid is an electric conductor used to distribute electric field and control a vacuum tube's electric current. It is placed between the cathode and anode and functions as an amplifier.