Valves or Tubes

Introduction to Valves

A vacuum tube, electron tube (in North America), or thermionic valve (elsewhere, especially in Britain) and Röhre in German (Adjective/Plural? Röhren as in Röhrenradio = Valve  Radio),  usually simply called "tube" or "valve", is a device that uses wires, grids and plates to change current flowing between the heated cathode (source) and collecting Anode. 

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