Tubes using the parametric principle, e.g. for parametric amplification

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Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons (details of transit-time tubes H01J23/00; particle accelerators H05H) > Travelling-wave tubes; Tubes in which a travelling wave is simulated at spaced gaps > Tubes using the parametric principle, e.g. for parametric amplification