Vacuum tube

A vacuum tube is an electronic device that controls the flow of electrical signals using a sealed glass or metal container with all air removed. Inside, it contains electrodes—such as a filament (cathode) that emits electrons when heated, and other elements like anodes and control grids—that guide and amplify electrical currents. By adjusting these components, vacuum tubes can amplify signals, switch currents on and off, or modify radio frequencies. Historically, they were fundamental in early electronics like radios and computers before being replaced by modern silicon-based components.