18WuD2x

no-charge machine fault time • noise current 477
no-charge machine fault time Unproductive computer
time resulting from errors or a malfunction.
nodal point See NODE.
node 1. The terminal point at which two or more
branches of a circuit meet, or a point that is
common to two circuits. 2. In a standing-wave
system, a zero point or minimum point, e.g.,
current node. Compare LOOP, 1. 3. A database
management system expression defining the
location of information about a record, user,
field, etc. 4. A point at which a satellite crosses
the equator. See also ASCENDING NODE, DE-
SCENDING NODE.
Node
Current
Displacement
node, 2
Node
nodules 1. Oxide particles that protrude above the
surface of magnetic tape. 2. In a planar pattern
describing radiation or pickup characteristics (as
for antennas, microphones, loudspeakers), a
small peak aligned in a direction other than that
of the main lobe.
no-field release In the starting box for a shunt motor,
the electromagnet that normally holds the
arm in full-running position; it is connected in series
with the field winding. When the field current
is lost, the arm is released, disconnecting the armature
for safety. Compare NO-VOLTAGE RE-
LEASE.
noise 1. A random-frequency current or voltage
signal extending over a considerable frequency
spectrum and having no useful purpose, unless
it is intentionally generated for test purposes.
2. Dissonant, interferential sound; unlike harmonious
sound, it is disagreeable. 3. In audio operations,
unwanted hiss and/or hum. 4. Extra bits
or bytes that must be removed from digital data
before it can be useful.
noise abatement The elimination or reduction of
noise intensity—especially a measure in a program
concerned with noise pollution in the environment.
noise analysis The measurement of the amplitude
and spectral distribution of noise and the determination
of its character.
noise analyzer An instrument for evaluating the
nature of noise in a communications system. See,
for example, NOISE METER. Noise analyzers are
sometimes adapted for vibration analysis.
noise-balancing system A bridge circuit inserted
between a receiver and antenna for balancing out
interferential signals resulting from nearby
power-line leaks or similar causes.
noise bandwidth Abbreviation, NBW. A figure obtained
by dividing the area under the poweroutput-vs.-frequency
curve of a device by the
power amplitude at the noise frequency of interest.
noise behind the signal Noise caused by, but exclusive
of, a signal.
noise blanker A device that cuts off one of the intermediate-frequency
stages of a radio receiver during
a noise pulse. The noise blanker is effective against
high-amplitude impulses of short duration.
noise-canceling antenna A specialized receiving
antenna system that uses two elements, one intended
for receiving primarily the desired signal(s)
and the other intended for receiving
primarily local human-made noise. The outputs
from the two elements are combined so that the
noise impulses appear out of phase, but of equal
amplitude. Because one element is located in a
favorable position for reception of desired signals
while the other element is not, the desired
signals do not cancel at the receiver input. As a
result, the signal-to-noise ratio is greatly
improved, compared with the use of the signal
antenna alone.
noise-canceling microphone A microphone that
discriminates against background sounds. It is
usually directional and relatively insensitive, requiring
the user to talk directly into it at close
range.
noise clipper A biased-diode circuit used as an
automatic noise limiter. The device cuts off all
signals above a predetermined amplitude on the
theory that noise peaks are high-level transients
in an otherwise uniform signal. Noise is reduced
at the sacrifice of system reproduction fidelity.
noise criteria An expression for the level of ambient
acoustic noise.
noise current Noise-generated current.