18WuD2x

unit record • universal-wound coil 711
contained within one storage medium, such as a
magnetic disk.
unitrivalent electrolyte An electrolyte, such as
sodium phosphate (Na 3 PO 4 ), that dissociates into
three univalent ions and one trivalent ion.
units position In a numbering system, the rightmost
position in a multidigit whole number; or, if
the number contains a radix point, the digit immediately
to the left of the radix point.
unit-step function See UNIT FUNCTION.
unitunnel diode A special form of semiconductor
diode, used as an oscillator at ultra-high and microwave
frequencies.
unit vector A vector that is 1 unit long in terms of
the scale representing a factor of interest, and
has the same direction as the vector of interest.
For example, if u is a unit vector, then 5u represents
a vector having the same direction and five
times the magnitude of u.
unity 1. The figure 1 implied. 2. A ratio of 1:1. 3. A
gain of 0 dB.
unity coupling Tight coupling between two coils,
the turns ratio often being 1 to 1 and the coils always
being closely interwound.
Input
unity coupling
Output
unity gain The condition in which the output amplitude
is the same as the input amplitude; that
is, a gain factor of 1, or 0 dB.
unity-gain bandwidth 1. For an active filter, the
bandwidth between the frequencies at which the
gain is 0 dB. 2. For an operational amplifier having
a rolloff of 6 dB per octave, the frequency at
which the open-loop gain is 0 dB.
uni-univalent electrolyte An electrolyte that dissociates
into two univalent ions [e.g., sodium
chloride (NaCl)].
univ Abbreviation of universal.
UNIVAC The name given to a family of digital computers
and data-processing systems. The name is
an acronym for Universal Automatic Computer.
univalent Having a valence of 1. For example, in the
compound sodium chloride (NaCl), the sodium ion
(Na+) and the chlorine ion (Cl–) are univalent.
universal bridge A bridge for the measurement of
capacitance (C), inductance (L), and resistance
(R). Such a bridge often is a skeletal foundation
circuit with a provision for plugging L, C, or R
standards in the various arms, as required. Also
called general-purpose bridge.
universal coordinated time Abbreviation, UTC.
Greenwich mean time coordinated by the International
Time Bureau for broadcast as signals
(on WWV, for example).
universal coupler 1. An arrangement of one or
more inductors and variable capacitors for
matching a transmitter to virtually any antenna.
One such device is the Collins coupler. 2. A device
for matching numerous generator output
impedances to numerous load impedances.
universal filter An active filter that is continuously
tunable over a wide frequency range and
that offers low-pass, high-pass, bandpass, and
band-suppression functions.
universal frequency counter A digital frequency
meter usable at radio and audio frequencies.
universal motor A small series-wound motor that
runs on direct current or single-phase alternating
current. This type of motor is used in many
household appliances and in motor-driven tools,
such as portable electric drills, polishers, etc.
universal output transformer An output transformer
having a number of taps on its primary
and secondary windings for use with a wide variety
of impedances.
universal product code Abbreviation, UPC. The
variable-width-bar code appearing on price tags
or product labels, and yielding such information
as cost, size, and color when read by supermarket
(or other retailer) optical characterrecognition
equipment. Also called universal
vendor marking (UVM).
universal receiver A radio receiver that can be operated
either from alternating current or direct
current (i.e., from utility power or battery power).
universal shunt See AYRTON-MATHER
GALVANOMETER SHUNT.
universal time See GREENWICH MEAN TIME.
universal transformer See UNIVERSAL OUTPUT
TRANSFORMER.
universal transmitter A radio transmitter that
can be operated either from alternating current or
direct current (i.e., from utility power or battery
power).
universal Turing machine In computer theory, a
TURING MACHINE capable of simulating other
Turing machines.
universal vendor marking See UNIVERSAL
PRODUCT CODE.
universal winding A zigzag winding used to reduce
the distributed capacitance of multilayer coils.
Also called lattice winding and honeycomb winding.
universal-wound coil A coil using a universal
winding. Such coils are common in intermediatefrequency
(IF) transformers and in radiofrequency
(RF) chokes.