18WuD2x

nonsynchronous vibrator • normal-mode rejection 483
VIBRATOR-TYPE RECTIFIER. Also see VIBRA-
TOR-TYPE POWER SUPPLY.
nontechnical Pertaining to circuits, devices, systems,
or phenomena described in lay terms, using
concise graphics and little or no mathematics. An
example is the simplified explanation of the operation
of a spread-spectrum radio transmitter.
nontonal components See NOISE, 3.
nontrigger voltage For a thyristor, the maximum
gate-to-cathode voltage that can be applied without
triggering the device. The amplitude of interferential
signals, including noise, must be below
this level to prevent accidental triggering.
nonuniform field An electric or magnetic field
whose intensity is not the same at all points.
nonvolatile memory Memory whose data is retained
even when power is removed for extended
periods. This type of memory requires no backup
power source. The main advantage of this type of
memory is the fact that the data is not lost in case
of a power interruption. Memory should not be
confused with storage. Magnetic, magnetooptical,
or optical disks (including hard drives) are
storage media, not memory. Memory data can be
stored and retrieved much faster than storage
data, because memory uses no mechanical parts.
Also see RANDOM-ACCESS MEMORY, READ-
ONLY MEMORY. Compare VOLATILE MEMORY.
nonvolatile storage A computer storage medium
in which the data does not require a source of
power to be retained. Examples: MAGNETIC
DISK, MAGNETIC TAPE, and COMPACT-DISK
READ-ONLY MEMORY.
no-op instruction An instruction that commands
a computer to perform no operation, other than
to proceed to the following instruction.
NOR circuit Also called NOT-OR CIRCUIT. In computer
and control operations, a circuit that delivers
a zero output signal, except when two or more
input signals are zero. The NOR circuit function
is the inverse of that of the OR circuit.
NOR gate A gate that performs the functions of a
NOR circuit.
norm The average or ambient condition.
A
B
A
0
0
1
1
B
0
1
0
1
C
1
0
0
0
NOR circuit
C
normal 1. Pertaining to the most commonly observed
set of conditions or parameters. 2. Standard.
3. Perpendicular; oriented at right angles.
4. Pertaining to a NORMAL DISTRIBUTION.
5. Pertaining to a NORMAL SOLUTION. 6. Pertaining
to an atom at its lowest energy state. See
NORMAL STATE OF ATOM.
normal curve See BELL-SHAPED CURVE.
normal distribution In a statistical evaluation, a
probability distribution represented by the socalled
bell-shaped curve. The maximum probability
occurs at the 50-percent value.
normal-distribution curve See BELL-SHAPED
CURVE.
normal electrode A standard electrode used in
electrode-potential measurements.
normal fault An unintended path between the hot
terminal of a load and ground.
normal fault plus grounded neutral fault A combination
of NORMAL FAULT and GROUNDED
NEUTRAL FAULT.
normal glow discharge In a glow-discharge tube,
the discharge region between the Townsend discharge
and the abnormal glow in which current
increases sharply, but a constant voltage drop is
maintained across the tube.
normal impedance A transducer’s input impedance
when the load impedance is zero.
normal induction curve A saturation curve for a
magnetic material. Also see BOX-SHAPED LOOP
and SATURABLE REACTOR.
normalize In computer programming, to use floating-point
numbers to modify the fixed-point part
of a number so that it is within a desired range.
normalized admittance The quantity 1/Z n , where
Z n is NORMALIZED IMPEDANCE.
normalized frequency The unitless number represented
by the ratio f/f r , where f r is a reference frequency
and f is a frequency of interest. Response
plots are sometimes conveniently drawn on the
basis of normalized frequency, the reference (or
resonant) frequency being indicated as 1, twice
the reference frequency as 2, etc.
normalized impedance A value of impedance divided
by the characteristic impedance of a waveguide.
normally closed Abbreviation, NC. Pertaining to a
switch or relay whose contacts are closed when
the device is at rest. Compare NORMALLY OPEN.
normally open Abbreviation, NO. Pertaining to a
switch or relay whose contacts are open when the
device is at rest. Compare NORMALLY CLOSED.
normal mode Pertaining to a device or system operated
in its usual or most common manner.
normal mode A state of acoustic resonance in an
enclosure, such as a speaker cabinet or a room.
normal-mode rejection Abbreviation, NMR. In a
digital direct-current voltmeter, the level of noise
on the applied voltage that will be rejected by the
instrument. Compare COMMON-MODE REJEC-
TION.