CONTROL GRIDThe electrode of a vacuum tube, other than a diode, upon which a signal voltage is
impressed to regulate the plate current.
DEFLECTION PLATESTwo pairs of parallel electrodes, one pair set forward of the other and at
right angles to each other, parallel to the axis of the electron stream within an electrostatic cathode-
DEIONIZATION POTENTIALThe potential at which ionization of the gas within a gas-filled tube
ceases and conduction stops, also referred to as extinction potential.
DIFFERENCE OF POTENTIALThe voltage existing between two points. It will result in the flow of
electrons whenever a circuit is established between the two points.
DIODEAn electron tube containing two electrode, a cathode, and a plate.
DIRECTLY HEATED CATHODEA wire, or filament, designed to emit electrons that flow from
cathode to plate. This is done by passing a current through the filament; the current heats the
filament to the point where electrons are emitted.
DISTORTIONAn undesired change in the waveform of the original signal, resulting in an unfaithful
reproduction of audio or video signals.
DOORKNOB TUBEAn electron tube that is similar to the acorn tube but larger. The doorknob tube is
designed to operate (at high power) in the uhf frequencies.
Ep-Ip CURVThe characteristic curve of an electron tube used to graphically depict the relationship
between plate voltage (Ep) and the plate current (Ip).
EDISON EFFECTAlso called Richardson Effect. The phenomenon wherein electrons emitted from a
heated element within a vacuum tube will flow to a second element that is connected to a positive
ELECTRON GUNAn electrode of a CRT that is equivalent to the cathode and control grid of
conventional tubes. The electron gun produces a highly concentrated stream of electrons.
ELECTROSTATIC DEFLECTIONThe method of deflecting an electron beam by passing it
between parallel charged plates mounted inside a cathode-ray tube.
FILAMENTThe cathode of a thermionic tube, usually a wire or ribbon, which is heated by passing
current through it.
FILTERA selective network of resistors, capacitors, and inductors that offer comparatively little
opposition to certain frequencies or to direct current, while blocking or attenuating other frequencies.
FIXED BIASA constant value of bias voltage.
FLEMING VALVEAn earlier name for a diode, or a two-electrode vacuum tube used as a detector.
FOCUSING ANODEAn electrode of a CRT that is used to focus the electrons into a tight beam.
FULL-WAVE RECTIFIERA circuit that uses both positive and negative alternations in an
alternating current to produce direct current.