H01J21/06—Tubes with a single discharge path having electrostatic control means only
H01J21/10—Tubes with a single discharge path having electrostatic control means only with one or more immovable internal control electrodes, e.g. triode, pentode, octode
H01J21/12—Tubes with variable amplification factor
H—ELECTRICITY
H01—ELECTRIC ELEMENTS
H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
H01J2893/00—Discharge tubes and lamps
H01J2893/0032—Tubes with variable amplification factor