By the late 1800s, the electrical revolution was well under way. Electrical power distribution systems were being deployed in urban areas. Electric lighting was rewriting the daily routine. Electric motors were being used in a wide range of household, industrial and transportation applications. Both wired and wireless telegraphy, and later, telephony, were enabling telecommunications.
Early electrical systems used electromechanical schemes to generate, control or amplify low frequency electrical signals. Their reliance on moving parts limited their speed, reduced their reliability and made it difficult to miniaturize them. By the 1920s, however, pioneers such as Thomson, Edison, Fleming, DeForest and Armstrong had overcome this limitation by contributing to the development of vacuum tube technology.
Unlike previous schemes, vacuum tubes used electrostatic, and in some cases, magnetic forces to directly control the flow of electrons from a negatively charged (and heated) cathode to a positively charged plate. By eliminating mechanical inertia, vacuum tubes were able to operate millions of times faster than electromechanical devices and made it possible to generate, amplify or control electrical signals up into the microwave region. The term ”electronics” was coined to describe the technologies associated with such devices.
Efforts to develop a solid state device that directly controls the flow of electrons without the inconvenience of heating a cathode or maintaining a vacuum envelope began in the 1930s. The first transistor was demonstrated in the late 1940s. Shortly thereafter, solid state devices began to replace vacuum tubes. With their ultra small size and capacity for economical manufacture using photolithography and related techniques, they ushered in a microelectronics revolution that continues to this day.
Although solid state devices predominate today, vacuum tubes still dominate in some niche applications such as microwave ovens. Also, many of the system and circuit design principles developed during the vacuum tube era by Armstrong and others live on in the solid state era and are still used by electrical engineers.
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The video embedded here comes from the AT&T Tech Channel’s archives.
Hand Made Vacuum Tubes by Claude Paillard – This present day video shows each step Mr. Paillard takes to construct his own vacuum tubes. |