Heptode definitions

Heptode

1) Vacuum tube
Found on https://www.crosswordclues.com/clue/heptode

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heptode

a seven-electrode electronic tube containing an anode, a cathode, a control electrode, and four additional electrodes
Found on http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=531-31-06

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Heptode

A heptode is a high-vacuum thermionic valve having seven electrodes, namely an anode, a cathode and five grids.
Found on http://www.probertencyclopaedia.com/browse/GH.HTM

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Heptode

A heptode is a high-vacuum thermionic valve having seven electrodes, namely an anode, a cathode and five grids. See also: Valve.
Found on https://www.encyclo.co.uk/local/20687

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