18WuD2x

708 unexpected halt • unidirectional response
Amplitude
Positive
half-cycles
Negative
half-cycles
unequal alternation
Time
unexpected halt During a computer program run,
an undirected (unplanned) halt (e.g., one caused
by a machine fault or program bug).
unfiltered Not having been subjected to filtering
action. An example is the pulsating-directcurrent
output of an alternating-current-operated
rectifier circuit.
unfocused light source In a photoelectric system,
a light source that delivers diffused light.
unformed rectifier A newly fabricated semiconductor
rectifier (especially selenium) or an electrolytic
rectifier before it has been electroformed
for improved characteristics.
unfurlable antenna An antenna that can be unrolled
to increase its length, thereby lowering its
fundamental resonant frequency; it can also be
rolled up to decrease its length and increase its
fundamental resonant frequency.
ungrounded item A component, circuit, or circuit
point having no connection to ground, except an
inadvertent one through common impedances or
leakage paths.
ungrounded system A system operated entirely
above ground, any path to ground being accidental.
unguided Without electronic guidance (pertaining
to missiles, rockets, satellites, etc.).
uni- A prefix (combining form) meaning one or single
and appearing in a number of electronic
terms. See the following several definitions for examples.
uniaxial 1. Having one axis. 2. Referred to one axis.
uniaxial crystal A crystal having one optical axis.
unibivalent electrolyte An electrolyte, such as
sodium carbonate (Na 2 CO 3 ), that dissociates into
two univalent ions and one bivalent ion.
Unicode Trade name for a 16- or 32-bit binary digital
code that allows for the representation of
characters and glyphs in all the written languages
of the world. The 16-bit code contains
65,536 code points; the 32-bit version contains
more than 1 million code points.
uniconductor cable A cable having a single conductor,
usually of braided or twisted wires.
uniconductor waveguide A waveguide consisting
of a metal sheath deposited on a solid dielectric
of cylindrical or rectangular cross
section.
unidentified flying object Abbreviation, UFO. An
object claimed to have been seen in flight, but not
identified by reliable authorities as any known
type of vehicle.
unidirect To commutate (see COMMUTATOR).
unidirectional 1. Flowing or acting in one direction
only. 2. Having a radiation or response sensitivity
that is maximum in primarily one
direction in space.
unidirectional antenna See UNIDIRECTIONAL
ARRAY.
unidirectional array A beam antenna that radiates
in one direction only, or principally in one direction,
unless rotated.
unidirectional conductivity Electrical conductivity
in only one direction; it characterizes an ideal
diode.
unidirectional coupler A directional coupler sampling
only one direction of transmission.
unidirectional current A current that flows always
in the same direction, although it might
fluctuate in intensity.
unidirectional elements Circuit elements, such
as diodes or transistors, that transmit energy in
only (or best in) one direction.
unidirectional field-effect transistor See UNI-
LATERAL FIELD-EFFECT TRANSISTOR.
unidirectional hydrophone An underwater unidirectional
microphone.
unidirectional loudspeaker A loudspeaker that
radiates sound substantially in one direction.
unidirectional microphone A microphone that receives
sound waves from one direction, usually
from the front, minimum response usually being
from the sides and back.
unidirectional network A network that transmits
signals in only one direction (i.e., the input and
output terminals are not interchangeable).
unidirectional pattern For a transducer (such as
an antenna, speaker, or microphone), a radiation
or response pattern that shows a pronounced
maximum in one direction only.
unidirectional pulse A single-polarity pulse.
unidirectional pulse train A series of unidirectional
pulses.
unidirectional response For a receiving transducer,
such as an antenna or microphone, a
response pattern that shows a pronounced
maximum in one direction only.