A klystron is a type of vacuum tube used to amplify radio frequency signals. It works by using a stream of electrons and a series of cavities to increase the power of the signal. Klystrons are commonly found in radar systems, satellite communications, and television broadcasting, where they help transmit high-frequency signals over long distances. The design of a klystron allows it to produce high output power and efficiency, making it essential in various applications. They are often used in conjunction with other devices, such as magnetrons and transmitters, to enhance signal quality and reach.