18WuD2x

202 display loss • distance-double law
seen by an operator using an output device with
the same receiver. Also called visibility factor.
display mode 1. A particular method of presenting
a display. For example, a character display on a
video unit might consist of bright characters on a
dark background, or dark characters on a light
background. 2. An operating mode for a particular
device, in which a display is used.
display module A self-contained unit with circuitry
and readouts for indicating a numerical
count.
display primaries Also called primary colors. In a
color television receiver, the colors red, green,
and blue. When mixed correctly, these three colors
can produce any visible hue.
display-storage tube A special cathode-ray tube in
which patterns and other information can be
stored for later viewing. The tube has two electron
guns: a writing gun and a reading (viewing) gun.
display unit A device that presents information for
visual reading. Included are analog and digital
meters, cathode-ray tubes, data printers, graphic
recorders, etc. Also see DISPLAY CONSOLE.
display visibility The ease with which a display
can be read by an operator.
display window 1. In a panoramic display, the
width of the presented frequency band in hertz.
2. The panel opening through which the indication
of a display unit appears.
displayed part That portion of a number displayed
in the readout of a calculator or computer. There
might be digits that are not displayed, but which
the machine might take into consideration
when making calculations. For example, in a
10-digit calculator display, the number
245.789378214895 would be displayed as
245.7893782. Depending on the calculator design,
the machine might truncate (disregard) the
undisplayed digits (14895), or take the undisplayed
digits into account when making calculations.
disposable component A circuit component or
machine part that is so inexpensive that it is
more cost-effective to discard it than to repair it
when it fails.
disruptive discharge Sudden, heavy current flow
through a dielectric material when it fails completely
under electric stress.
dissector A transducer that samples an illuminated
image point by point.
dissector tube A camera tube using a flat photocathode,
upon which the image is focused by the
lens system. Electromagnetic deflection from
external coils provides scanning. Electrons pass
sequentially from the image cathode to a scanning
tube at the opposite end of the camera tube.
Also called Farnsworth dissector tube and orthiconoscope.
dissipation 1. The consumption of power, often
without contributing to a useful end, and usually
accompanied by the generation of heat. 2. In an
Object
amplifier, the difference between the collector,
drain, or plate input power and the usable output
power.
dissipation constant For a thermistor, the ratio of
the change in power dissipation to a corresponding
change in body temperature.
dissipation factor 1. For a dielectric material, the
tangent of the dielectric loss angle. Also called
loss tangent. 2. Symbol, D. For an impedance
(such as a capacitor), the ratio of resistance to reactance;
D = R/X. It is the reciprocal of the figure
of merit (Q).
dissipation line A resistive section of transmission
line, used for dissipating power at a certain
impedance. Two parallel lengths of resistance
wire are terminated by a large, noninductive resistor
that has a value equal to the characteristic
impedance of the line.
dissipator
Optics
Anode
dissector tube
Aperture
Image
dc
Input
Output
dc
Input
Photocathode
1. A device used primarily to consume
power (i.e., a power sink). 2. A device for removing
heat generated by a device’s operation (e.g., a
heatsink attached to a power transistor).
dissociation The condition that characterizes electrolytes
(certain acids, bases, or salts in water solution)
in which the molecules of the material
break up into positive and negative ions.
dissonance The unpleasant effect (especially in
music) produced by nonharmonious combinations
of sounds.
dissymmetrical network A network having unequal
input and output image impedances.
dissymmetrical transducer A transducer having
unequal input and output image impedances.
distance-double law A theoretical rule for determining
the rate at which sound intensity decreases
as distance increases. Under ideal
conditions, when the distance from a sound
source is doubled, the sound pressure is reduced
to one-fourth of its original level, a reduction
of 6 decibels. This is analogous to the
inverse-square law for visible light and other radiant
energy.