18WuD2x

uranium rays • UVM 715
observed that uranium salts emit rays (later identified
as alpha, beta, and gamma) that can pass
through bodies opaque to light and are capable of
exposing a photographic plate. Also called Becquerel
rays.
urea formaldehyde resin A thermosetting, synthetic
resin used in the manufacture of a number
of plastic dielectric bodies and formed by the reaction
of urea with formaldehyde.
urea plastic Any of several thermosetting plastics
having a urea base and used as a dielectric and
as a molding material in electronics (e.g., urea
formaldehyde resin).
URSI Abbreviation of Union Radio Scientifique Internationale
(International Radio Scientific Union).
ursigram A broadcast message giving information
on sunspots, radio propagation, terrestrial magnetism,
and related subjects. Also see URSI.
usable frequency 1. Any frequency at which communications
can be maintained between two
points via ionospheric propagation. 2. Any frequency
at which a communications system is operational.
usable sample 1. The portion of an oscilloscope or
monitor display that is visible on the screen. 2. In
statistics, a sample that is considered valid for
calculation purposes.
USB Abbreviation of UPPER SIDEBAND.
user friendliness 1. For electronic equipment and
systems, the quality of being easy for people to
operate. 2. The relative ease with which a machine,
especially a computer, can be operated by
people.
useful life The elapsed time between the installation
of an expendable component, circuit, or system,
and the time it must be replaced.
useful line In television, the portion of a scanning
line that can be used for picture signals. Also
called AVAILABLE LINE.
user group A group of hobbyists or company representatives
having in common the ownership
and/or use of a specific brand of computer, and
who meet or otherwise interact to share their expertise
with, or programs, for, the machine. Also
applicable to similar groups of programmablecalculator
owners.
user’s library A compilation of programs supplied
to (by the vendor) or generated by a user group.
USM Abbreviation of underwater-to-surface missile.
USSC Abbreviation of UPPER SIDEBAND, SUP-
PRESSED CARRIER.
UTC Abbreviation of UNIVERSAL COORDINATED
TIME.
utility 1. An organization providing a public service,
such as electric power or electronic communications.
2. In computer operations, a program
or set of programs intended for diagnosing
and/or correcting hardware and software problems.
utility box A general-purpose aluminum or steel
box, supplied in various convenient sizes (painted
or unpainted), used as a housing or shield for
electronic equipment.
utility factor For a transformer used in a directcurrent
(dc) power supply, the ratio of dc output
to required kilovolt-ampere (kVA) capacity.
utilization factor See UTILITY FACTOR.
UTL Abbreviation of unit transmission loss.
UUM Abbreviation of underwater-to-underwater
missile.
UV 1. Abbreviation of ULTRAVIOLET. 2. Abbreviation
of UNDERVOLTAGE.
Uvicon A television camera tube in which a conventional
vidicon scanning section is preceded
by an ultraviolet-sensitive photocathode, an
electron-accelerating section, and a special target.
Uviol lamp An ultraviolet lamp using uviol glass—
a special glass that is transparent to ultraviolet
rays.
UVM Abbreviation of UNIVERSAL VENDOR
MARKING.