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AI-3
GETTER—An alkali metal introduced into a vacuum tube during manufacture. It is fired after the tube
has been evacuated to react chemically with (and eliminate) any remaining gases.
GRID BIAS—A constant potential applied between the grid and cathode of a vacuum tube to establish an
operating point.
GRID CURRENT—The current that flows in the grid-to-cathode circuit of a vacuum tube.
GRID-LEAK BIAS—A high resistance connected across the grid capacitor or between the grid and
cathode. It provides a dc path to limit the accumulation of a charge on the grid.
HALF-WAVE RECTIFIER—A rectifier using only one-half of each cycle to change ac to pulsating dc.
HEATER—Same as a filament.
HORIZONTAL-DEFLECTION PLATES—A pair of parallel electrodes in a CRT that moves the
electron beam from side to side.
IMPLOSION—The inward bursting of a CRT due to high vacuum. The opposite of explosion.
INDIRECTLY HEATED CATHODE—Same as a directly heated cathode with one exception: The hot
filament raises the temperature of the sleeve around the filament; the sleeve then becomes the
electron emitter.
INTERELECTRODE CAPACITANCE—The capacitance between one electron-tube electrode and the
next electrode toward the anode.
IONIZATION—The electrically charged particles produced by high energy radiation, such as light or
ultraviolet rays, or by the collision of particles during thermal agitation.
IONIZATION POINT—The potential required to ionize the gas of a gas-filled tube. Sometimes called
firing point.
LIGHTHOUSE TUBE—An electron tube shaped like a lighthouse, is designed to handle large amounts
of power at uhf frequencies.
LINEAR—Having an output that varies in direct proportion to the input.
MULTI-ELECTRODE TUBE—An electron tube that is normally classified according to the number of
grids. (The multi-electrode tube contains more than three grids).
MULTI-UNIT TUBE—An electron tube containing two or more units within the same envelope. The
multi-unit tube is capable of operating as a single-unit tube or as separate tubes.
NONLINEAR—Having an output that does not rise of fall directly with the input.
OILCAN TUBE—A type of planar tube, similar to the lighthouse tube, which has cooling fins. The
oilcan tube is designed to handle large amounts of power at uhf frequencies.
PEAK CURRENT—The maximum current that flows during a complete cycle.
PEAK-REVERSE VOLTAGE—The peak ac voltage which a rectifier tube will withstand in the reverse
direction.
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