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information superhighway • inherited error 365
tionary satellites, and low-earth-orbit (LEO) satellite
systems.
information word A character group representing
stored information and managed, as a unit, by
hardware or software.
infra- Prefix meaning below or lower than (e.g., IN-
FRARED).
infrablack region In a composite video signal, the
blacker-than-black region (see BLACKER THAN
BLACK).
infradyne receiver A superheterodyne receiver in
which the intermediate frequency is the sum of
the signal and oscillator frequencies, rather than
their (usual) difference.
infrared Pertaining to electromagnetic energy in a
band whose wavelength is longer than that of visible
light, but shorter than that of microwave energy.
infrared communication Communication by keying
or modulating infrared rays.
infrared counter-countermeasure A military tactic
in which action is taken against an enemy infrared
countermeasure.
infrared countermeasure A military tactic using
countermeasure methods to cripple enemy infrared
equipment.
infrared detector A device that senses the presence
of infrared energy. Some such detectors are
bolometers, radiometers, radiomicrometers, and
photocells.
infrared-emitting diode Abbreviation, IRED. A
semiconductor diode, such as the galliumarsenide
type, that emits infrared rays when a
current passes through the p-n junction in the
forward direction.
infrared guidance A navigation and reconnaissance
system using infrared rays.
infrared homing The method whereby a guided
missile uses infrared rays to guide it to its target.
infrared light See INFRARED RAYS.
infrared motion detector See MOTION DETEC-
TOR and INFRARED.
infrared photography Photography in which the
scene is illuminated with infrared light or emits
infrared rays, and the film is infrared sensitive.
infrared radiation See INFRARED RAYS.
infrared rays Radiation at frequencies in the IN-
FRARED region. Also (somewhat mistakenly)
called heat rays.
infrared remote control 1. The use of an infrared
link, usually over short line-of-sight distances,
for the purpose of controlling the operation of
electronic equipment. A common example is the
local remote control of a television receiver or
high-fidelity system. 2. A small box, containing
buttons, a transmitter and an infrared-emitting
diode (IRED), used for local remote control of devices,
such as television receivers and highfidelity
sound systems.
infrared spectrum The region of the electromagnetic
spectrum in which INFRARED radiation is
found. This band lies between the microwave radio
spectrum and the visible-light spectrum.
infrared therapy The use of infrared rays by
physicians and other practitioners to treat certain
disorders.
infrared waves Electromagnetic waves whose
lengths are greater than those of visible light
waves, but less than those of microwaves.
infrared window Any portion of the infrared spectrum
in which energy is easily transmitted
through the lower atmosphere of the earth.
infrasonic Pertaining to acoustic disturbances
whose frequencies are below the range of human
hearing (less than about 20 Hz).
infrasonic intrusion detector A system that detects
the presence of extremely low-frequency
acoustic disturbances, and sends a signal to an
alarm. Such INFRASONIC waves can be caused
by various actions such as walking on a wooden
floor, opening or closing a door, etc.
infrasonics The branch of physics dealing with IN-
FRASONIC phenomena.
infrasound Acoustic disturbances in the air,
whose frequencies are lower than about 20 Hz,
and whose wavelengths are longer than about 55
feet (17 meters).
inharmonic distortion Distortion in which the frequencies
of extraneous components are not harmonically
related to the fundamental frequency.
It is sometimes experienced when a tone-burst
signal is applied to a loudspeaker.
Max.
Amplitude
Min.
0 1 2 3
Frequency, kHz
Fundamental
inharmonic distortion
inherent component A (usually extraneous) property
possessed by a device because of its internal
peculiarities. Thus, an inductor has inherent capacitance;
a capacitor has inherent inductance.
inherited error In an extended calculation, an error
carried through from one of the earlier steps.