Definition
A vacuum tube is an electronic device used to amplify, switch, or modify electrical signals. It consists of a glass or metal enclosure with electrodes inside, from which air has been removed to create a vacuum. Electrons flow through the vacuum, controlled by the electrodes. Once a staple in radios, televisions, and early computers, vacuum tubes have largely been replaced by transistors and integrated circuits. Think of them as the bulky ancestors of modern microchips. They converted DC to AC power, amplifying signals.