A century of electronics [the evolution of vacuum tubes]

This article traces the evolution of vacuum tubes (thermionic valves) from their origins in incandescent filament lamps. It details the use of diodes and triodes in early radio transmission and detection, being the building blocks of rectifiers, amplifiers and oscillators. It also mentions the later developments of tetrodes and pentodes and concludes that the end of the vacuum tube era began with the introduction of the point contact transistor.