AI-2
CONTROL GRID—The electrode of a vacuum tube, other than a diode, upon which a signal voltage is
impressed to regulate the plate current.
DEFLECTION PLATES—Two 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-
ray tube.
DEIONIZATION POTENTIAL—The potential at which ionization of the gas within a gas-filled tube
ceases and conduction stops, also referred to as extinction potential.
DIFFERENCE OF POTENTIAL—The voltage existing between two points. It will result in the flow of
electrons whenever a circuit is established between the two points.
DIODE—An electron tube containing two electrode, a cathode, and a plate.
DIRECTLY HEATED CATHODE—A 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.
DISTORTION—An undesired change in the waveform of the original signal, resulting in an unfaithful
reproduction of audio or video signals.
DOORKNOB TUBE—An 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 CURV—The characteristic curve of an electron tube used to graphically depict the relationship
between plate voltage (Ep) and the plate current (Ip).
EDISON EFFECT—Also 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
potential.
ELECTRON GUN—An 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 DEFLECTION—The method of deflecting an electron beam by passing it
between parallel charged plates mounted inside a cathode-ray tube.
FILAMENT—The cathode of a thermionic tube, usually a wire or ribbon, which is heated by passing
current through it.
FILTER—A 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 BIAS—A constant value of bias voltage.
FLEMING VALVE—An earlier name for a diode, or a two-electrode vacuum tube used as a detector.
FOCUSING ANODE—An electrode of a CRT that is used to focus the electrons into a tight beam.
FULL-WAVE RECTIFIER—A circuit that uses both positive and negative alternations in an
alternating current to produce direct current.
