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Publication of BE441216ApublicationCriticalpatent/BE441216A/xx
H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
H01J1/02—Main electrodes
H01J1/13—Solid thermionic cathodes
H01J1/15—Cathodes heated directly by an electric current
H01J1/16—Cathodes heated directly by an electric current characterised by the shape