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Publication of BE403213ApublicationCriticalpatent/BE403213A/xx
H01J17/00—Gas-filled discharge tubes with solid cathode
H01J17/50—Thermionic-cathode tubes
H01J17/52—Thermionic-cathode tubes with one cathode and one anode
H01J17/54—Thermionic-cathode tubes with one cathode and one anode having one or more control electrodes
H01J17/56—Thermionic-cathode tubes with one cathode and one anode having one or more control electrodes for preventing and then permitting ignition, but thereafter having no control