Initial version

# [TECH] Vacuum Tube Electronics
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**Vacuum Tubes** (thermionic valves) were the first electronic amplifiers and switching devices, enabling radio, radar, television, and early digital computers.
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## Overview
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John Ambrose Fleming's diode (1904) and Lee de Forest's triode Audion (1906) allowed amplification of weak electrical signals — a capability unavailable with purely passive components. Vacuum tubes enabled long-distance telephone repeaters, radio transmitters, radar systems, and the first electronic computers (ENIAC, 1945: 18,000 tubes). The vacuum tube was the dominant active electronic component until replaced by transistors (1947–1960).
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AT&T Bell Labs and RCA developed most of the key tube technologies and the manufacturing infrastructure that later transitioned to transistors and integrated circuits.
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## Key Actors
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- **Companies**: Western Electric/AT&T, RCA (Radio Corporation of America, 1919), General Electric, Philips
- **Inventors**: John Ambrose Fleming (1849–1945), Lee de Forest (1873–1961)
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## Key Patents
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- Fleming, J.A. GB Patent 24,850 (1904) — thermionic diode
- de Forest, L. US Patent 879,532 (1908) — triode Audion
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## Economic Value
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Vacuum tubes were a ~$1B/year industry at peak (1950s). More importantly, they enabled radio (now $150B+/year), early computing, and the institutional infrastructure (Bell Labs, RCA) that produced transistors and ICs.
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## Notes
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The vacuum tube industry is now minimal (audiophile equipment, microwave sources). Its historical enabling value is captured in the industries it spawned. Bell Labs alone produced 9 Nobel Prizes and inventions worth trillions.
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# Parents
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* [SCI] Electromagnetic Wave Theory⏎