18WuD2x

678 temperature gradient • terrain echoes
temperature gradient A range of temperature
variation, such as the rate of change of temperature,
with respect to change of power dissipation,
or the rate of change of temperature with spatial
displacement.
temperature inversion See INVERSION, 1.
temperature meter An indicator (usually a directcurrent
voltmeter or millivoltmeter) whose scale
reads directly in degrees.
temperature scale See THERMOMETER SCALE.
temperature-sensitive resistor See THERMIS-
TOR.
temperature shock See THERMAL SHOCK.
temperature-to-voltage converter A circuit or device,
such as a thermocouple, that delivers an
output voltage proportional to an applied temperature.
template 1. A diagram, usually drawn on paper, to
show the locations at which components should
be placed or tasks should be performed. It is
taped or cemented temporarily to the work, and
the points are transferred to the latter by prickpunching.
2. A stencil-like plate with alphanumeric
and circuit symbols, used as a drafting aid.
Sometimes called “drafting stencil.”
temporary magnet 1. A body that exhibits magnetism
only briefly after it has been exposed to
another magnet. Compare PERMANENT MAG-
NET. 2. See ELECTROMAGNET.
temporary storage 1. In computer and data-processing
operations, the storage of data or instructions
only until they are needed. Also called
INTERIM STORAGE. 2. Locations in a computer
memory set aside during a program run for holding
intermediate results of operations.
TEM wave See TRANSVERSE ELECTROMAG-
NETIC WAVE.
ten code A set of abbreviations used by two-way
radio operators. Each “ten signal” represents a
specific statement or query.
tension 1. A force that tends to stretch, pull tight,
or pull apart. Compare STRAIN. 2. A term referring
to VOLTAGE—especially in a utility power
transmission line.
ten-turn potentiometer A precision potentiometer
whose shaft must be turned through 10 complete
revolutions to cover the entire resistance
range. Also see HELICAL POTENTIOMETER and
MULTITURN POTENTIOMETER.
T-equivalent circuit See TEE-EQUIVALENT CIR-
CUIT.
tera- Abbreviation, T. 1. A prefix meaning
trillion(s), (i.e., 10 12 ). 2. A prefix meaning 2 40 .
tera-electronvolt Abbreviation, TeV. A large unit
of energy; 1 TeV = 10 12 electronvolts. Also see
ELECTRONVOLT.
terahertz Abbreviation, THz. A unit of extremely
high frequency equal to 10 12 Hz. Also called Fresnel.
teraohm A unit of high resistance, reactance, or
impedance equal to 10 12 ohms.
terawatt Abbreviation, TW. A large unit of power;
1 TW = 10 12 W.
terbium Symbol, Tb. A metallic element of the
rare-earth group. Atomic number, 65. Atomic
weight, 158.93.
terbium metals A group of rare-earth metals, including
europium, gadolinium, terbium, and occasionally
dysprosium.
term In an algebraic expression, constants, variables,
or combinations of these, separated by operation
signs (e.g., the expression 4xy + z has two
terms).
terminal 1. A connection point at the input, output,
or an intermediate point of a device, or a
point at which a voltage is to be applied. 2. A
metal tab or lug attached to the end of a lead for
connection purposes. 3. Pertaining to the end of a
series of events, etc. (e.g., terminal tests). 4. In a
data-communications system, a point of data input
or output. Also called data terminal. If it does
not have computing capability of its own, it is often
called a dumb terminal.
terminal block A group of several terminals, intended
for interconnection of circuits, mounted
on a solid insulating block.
terminal board An insulating board carrying several
lugs, tabs, or screws as terminals (see TER-
MINAL, 2). Also see TERMINAL STRIP.
terminal guidance The navigation of a missile or
aircraft to help it reach its target or destination.
terminal impedance The internal impedance of a
device measured at the input or output terminals.
terminal point of degradation The point at which
degradation of a circuit or component is complete.
Also see DEGRADATION FAILURE.
terminal repeater A telephone repeater operated
at the end of a line.
terminal strip A strip of insulating material, such
as plastic or ceramic, on which are mounted one
or more screws, lugs, or other terminals. Also see
TERMINAL, 2.
terminal strip (lug-type)
terminal voltage The voltage at the output terminals
of an unloaded battery or generator.
ternary code See TRINARY NUMBER SYSTEM.
ternary fission The splitting of an atomic nucleus
into three nuclear pieces. Also see FISSION.
ternary number system See TRINARY NUMBER
SYSTEM.
terrain echoes Radar images caused by reflections
from hills, mountains, and other natural terrestrial
surface features. Also see GROUND
CLUTTER.