Glossary:Valve: Difference between revisions
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Latest revision as of 15:09, 21 March 2019
A thermionic valve or vacuum tube is an amplifying device consisting of a glass tube containing several electrodes in a vacuum. An electrically heated cathode emits electrons which are attracted by an anode. Their flow is controlled by the voltage on a wire mesh grid in their path. Long since superseded by much smaller and less power-hungry transistors in all but a few niche applications.