ABRASIVITY - The ability of the magnetic tape to wear the head.
ABSORPTION - (1) Dissipation of radio or sound waves as they interact with
matter. (2) The absorbing of light waves without reflection or refraction .
ABSORPTION, LAW OF - In Boolean algebra, the law which states that the odd
term will be absorbed when a term is combined by logical multiplication with the logical
sum of that term and another term, or when a term is combined by logical addition with the
logical product of one term and another term (for example, A(A + B) = A + AB = A) .
ABSORPTION WAVEMETER - An instrument used to measure audio frequencies .
ABSORPTION WAVEMETER - A device used for measuring frequency, consisting
of a tuned circuit or cavity that is loosely coupled to the frequency being measured.
Maximum energy is absorbed at the resonant frequency.
ACCELERATING ANODE - An electrode charged several thousand volts positive
and used to accelerate electrons toward the front of a cathode-ray tube .
ACCELERATION SERVOSYSTEM - A servosystem that controls the acceleration
(rate of change in velocity) of a load .
ACCELEROMETER - A device that measures the acceleration to which it is
subjected and develops a signal proportional to it .
ACCEPTOR IMPURITY - An impurity which, when added to a semiconductor,
accepts one electron from a neighboring atom and creates a hole in the lattice structure
of the crystal. Also called TRIVALENT IMPURITY .
ACCESS TIME - The amount of time between the time a request for data from
a storage device is made and the time the data is delivered.
ACORN TUBE - A very small tube with closely spaced electrodes and no base.
The tube is connected to its circuits by short wire pins that are sealed in a glass or
ceramic envelope. The acorn tube is used in low-power uhf circuits .
ACOUSTICS - The science of sound .
ACQUISITION - Operational phase of a fire-control or track radar during
which the radar system searches a small volume of space in a prearranged pattern .
ACTIVE SATELLITE - A satellite that amplifies the received signal and
retransmits it back to earth .
ACTUATOR - The part of a switch that is acted upon to cause the switch to
change contact connections; for example, toggle, pushbutton, and rocker .
ADA - A high-level programming language designed by the Department of
Defense.
ADDITIVE - Any material in the coating of magnetic tape other than the
oxide and binder resins. (Examples: plasticizers (to soften an otherwise hard or brittle
binder), lubricants (to lower the coefficient of friction of an otherwise high-friction
binder), fungicides (to prevent fungus growth), dispersants (to uniformly distribute the
oxide particles), and dyes.)
AFDS - An abbreviation for the amphibious flagship data system .
AIR-CONTROL PANEL - Panel that monitors the dry-air input at each user
equipment .
AIR-CORE TRANSFORMER - A transformer composed of two or more coils that
are wound around a nonmetallic core .
ALLOWANCE PARTS LIST (APL) - Repair parts required for units having the
equipment/ component listed .
ALLOYED JUNCTION - A junction formed by recrystallization of a molten
region of P-type material on an N-type substrate, or vice versa .
ALPHA - The emitter-to-collector current gain in a common-base circuit .
ALPHAMERIC (ALPHANUMERIC) CHARACTER SET - The set of characters that
includes letters, numbers, and special characters.
ALTERNATING CURRENT - An electrical current that constantly changes
amplitude and changes polarity at regular intervals .
ALTERNATING CURRENT (ac) BIAS - (1) The alternating current, usually of a
frequency several times higher than the highest input signal frequency, that is fed to a
record head in addition to the input signal current. (2) Linearizes the recording process.
(3) Is universally used in direct analog recording.
ALTITUDE - The vertical distance of an aircraft or object above a given
reference, such as ground or sea level .
ALUMINUM CREEP - (1) The movement of aluminum wire from a point where
pressure is applied. (2) The "retreat" of heated aluminum wire as it cools .
AMBIENT TEMPERATURE - The surrounding temperature such as the temperature
of air surrounding a conductor in a compartment or within a piece of equipment .
AMBIGUOUS RETURNS - Echoes that exceed the prt of a radar and appear at
incorrect ranges .
AMERICAN WIRE GAUGE (AWG) - The standards adopted in the United States for
the measurement of wire sizes .
AMMETER - An instrument for measuring the amount of electron flow (in
amperes) .
AMPERE - The basic unit of electrical current .
AMPERE-TURN - The magnetomotive force developed by 1 ampere of current
flowing through a coil of one turn .
AMPERITE (BALLAST) TUBE - A current-controlling resistance device designed
to maintain substantially constant current over a specified range of variation in applied
voltage or resistance of a series circuit .
AMPLIDYNE - A special dc generator in which a small dc voltage applied to
field windings controls a large output voltage from the generator. In effect, an amplidyne
is a rotary amplifier that often times produces gain of approximately 10,000 .
AMPLIFICATION - (1) The process of enlarging a signal in amplitude (as of
voltage or current) . (2) The ratio of output magnitude to input magnitude in a device
that is intended to produce an output that is an enlarged reproduction of its input .
AMPLIFICATION FACTOR - The voltage gain of an amplifier with no load on
the output .
AMPLIFIER - The device that provides amplification (the increase in
current, voltage, or power of a signal) without appreciably altering the original signal .
AMPLITRON - See CROSS-FIELD AMPLIFIER .
AMPLITUDE - The size of a signal as measured from a reference line to a
maximum value above or below the line. Generally used to describe voltage, current, or
power .
AMPLITUDE DISTORTION - Distortion that is present in an amplifier when the
amplitude of the output signal fails to follow exactly any increase or decrease in the
amplitude of the input signal .
AMPLITUDE/FREQUENCY RESPONSE - (See frequency response.)
AMPLITUDE MODULATION - Any method of varying the amplitude of an
electromagnetic carrier frequency in accordance with the intelligence to be transmitted .
AMPLITUDE STABILITY - Amplitude stability refers to the ability of the
oscillator to maintain a constant amplitude in the output waveform .
ANALOG COMPUTER - A computer that solves problems using continuous data
from physical quantities like voltage or temperature.
ANALOG RECORDING - A method of recording in which some characteristic of
the record current, such as amplitude or frequency, is continuously varied in a manner
similar to the variations of the original signal.
AND CIRCUIT - See AND GATE .
AND GATE - (1) An electronic gate whose output is energized only when
every input is in its prescribed state. An AND gate performs the function of the logical
"AND"; also called an AND circuit. (2) A binary circuit, with two or more inputs
and a single output, in which the output is a logic 1 only when all inputs are a logic 1
and the output is a logic 0 when any one of the inputs is a logic 0 .
ANGLE MODULATION - Modulation in which the angle of a sine-wave carrier is
varied by a modulating wave .
ANGLE OF INCIDENCE - The angle between the incident wave and the normal .
ANGLE OF INCLINATION - The angular difference between the equatorial plane
of the earth and the plane of orbit of the satellite .
ANGLE OF REFLECTION - The angle between the reflected wave and the normal
.
ANGLE OF REFRACTION - The angle between the normal and the path of a wave
through the second medium .
ANGSTROM UNIT - The unit used to define the wavelength of light waves .
ANISOTROPIC - The property of a radiator that allows it to emit strong
radiation in one direction .
ANODE - (1) A positive electrode of an electrochemical device (such as a
primary or secondary electric cell) toward which the negative ions are drawn [6) . (2) The
semiconductor-diode terminal that is positive with respect to the other terminal when the
diode is biased in the forward direction .
ANTENNA - A conductor or set of conductors used to radiate rf energy into
space or to collect rf energy from space or to do both .
ANTENNA BEAM WIDTH - Width of a radar beam measured between half-power
points .
ANTENNA COUPLER - A device used for impedance matching between an antenna
and a transmitter or receiver .
ANTENNA SYSTEM - Routes rf energy from the transmitter, radiates the
energy into space, receives echoes, and routes the echoes to the receiver .
ANTIJAMMING CIRCUIT - An electronic circuit used to minimize the effects
of enemy countermeasures, thereby permitting radar echoes to be visible on the indicator .
ANTISEIZE COMPOUND - A silicon-based, high-temperature lubricant applied
to threaded components to aid in their removal after they have been subjected to rapid
heating and cooling .
ANTITRANSMIT-RECEIVE TUBE (atr) - A tube that isolates the transmitter
from the antenna and receiver. Used in conjunction with a tr tube .
APERTURE - See SLOT .
APOGEE - The point in the orbit of a satellite the greatest distance from
the earth .
APPARENT DRIFT - The effect of the earth's rotation on a gyro that causes
the spinning axis to appear to make one complete rotation in one day. Also called APPARENT
PRECESSION or APPARENT ROTATION .
APPARENT POWER - That power apparently available for use in an ac circuit
containing a reactive element. It is the product of effective voltage times effective
current expressed in volt-amperes. It must be multiplied by the power factor to obtain
true power available .
APPARENT PRECESSION - See APPARENT DRIFT .
APPARENT ROTATION - See APPARENT DRIFT .
APPLICATION (PROGRAMS) SOFTWARE - Programs written to solve user problems.
ARC EXTINGUISHER - The part of a circuit breaker that confines and divides
the arc which occurs when the contact of the circuit breaker opens .
ARITHMETIC-LOGIC UNIT - The part of the cpu that contains the logic
capability and performs all the arithmetic functions (addition, subtraction,
multiplication, and division).
ARMATURE - (1) In a relay, the movable portion of the relay . (2) The
windings in which the output voltage is generated in a generator or in which input current
creates a magnetic field that interacts with the main field in a motor .
ARMATURE LOSSES - Copper losses, eddy current losses, and hysteresis
losses that act to decrease the efficiency of armatures .
ARMATURE REACTION - The effect in a dc generator of current in the
armature creating a magnetic field that distorts the main field and causes a shift in the
neutral plane .
ARRAY OF ARRAYS - Same as COMBINATION ARRAY .
ARTIFICIAL INTELLIGENCE - The capability of a machine to perform
human-like intelligence functions, such as learning, adapting, reasoning, and
self-correction.
ARTIFICIAL TRANSMISSION LINE - An LC network that is designed to simulate
characteristics of a transmission line .
ASBESTOS - A noncombustible, nonconductive, fiber-like mineral used as an
insulating material .
ASBESTOSIS - Fibrosis of the lungs caused by inhalation of asbestos fibers
.
ASCII (American Standard Code for Information Interchange) - A
standardized 8-bit code (originally a 7-bit code) designed for transmitting and processing
data.
A-SCOPE - A radar display on which slant range is shown as the distance
along a horizontal trace .
ASSEMBLER - A computer program that translates source programs written in
assembly language into machine language (object) programs.
ASSEMBLY - A number of parts or subassemblies, or any combination thereof,
joined together to perform a specific function .
ASSEMBLY LANGUAGE - A low-level, machine-oriented programming language in
which each instruction (written as a mnemonic) translates into a single machine language
(computer) instruction.
ASTABLE MULTIVIBRATOR - A multivibrator that has no stable state. Also
called free-running because it alternates between two different output voltage levels
during the time it is on. The frequency is determined by the RC time constant of the
coupling circuit .
ASWTDS - An abbreviation for the antisubmarine warfare tactical data
system .
ASYMMETRICAL MULTIVIBRATOR - A multivibrator that generates rectangular
waves .
ASYNCHRONOUS - The teletypewriter operation where the transmitter and
receiver do not operate continuously .
ASYNCHRONOUS ORBIT - One where the satellite does not rotate or move at
the same speed as the earth .
ATDS - An abbreviation for the airborne tactical data system .
ATTENUATION - The ability of a filter circuit to reduce the amplitude of
unwanted frequencies to a level below that of the desired output frequency .
ATTRACTION - The force that tends to make two objects approach each other.
Attraction exists between two unlike magnetic poles (north and south) or between two
unlike static charges .
AUDIO AMPLIFIER - An amplifier designed to amplify frequencies between 15
hertz (15 Hz) and 20 kilohertz (20 kHz) .
AUDIO-FREQUENCY-TONE SHIFT - A system that uses amplitude modulation to
change dc mark and space impulses into audio impulses .
AUTOMATIC DATA PROCESSING (ADP) - A general term used to define a system
for automatically performing a series of data processing functions by means of machines
using mechanical, electromechanical, and electronic circuitry.
AUTOMATIC GAIN CONTROL - A circuit used to vary radar receiver gain for
best reception of signals that have widely varying amplitudes .
AUTOMATIC TRACKING - Tracking done by equipment that compares the
direction of the antenna axis and the direction of the received signal and uses the
difference (error) signal to reposition the antenna .
AUTOMATIC VOLUME/GAIN CONTROL - A circuit used to limit variations in the
output signal strength of a receiver .
AUXILIARY EQUIPMENT - The peripheral equipment or devices that may or may
not be in direct communication with the central processing unit of a computer.
AUXILIARY STORAGE - See storage, secondary.
AVALANCHE EFFECT - A reverse breakdown effect in diodes that occurs at
reverse voltages beyond 5 volts. The released electrons are accelerated by the electric
field, which results in a release of more electrons in a chain or "avalanche"
effect .
AVERAGE POWER - (1) The peak power value averaged over the
pulse-repetition time . (2) Output power of a transmitter as measured from the start of
one pulse to the start of the next pulse .
AVERAGE VALUE (OF AC) - The average of all the instantaneous values of
one-half cycle of alternating current .
AXIS - A straight line, either real or imaginary, passing through a body
around which the body revolves .
AZIMUTH - Angular measurement in the horizontal plane in a clockwise
direction .
AZIMUTH ALIGNMENT - The alignment of the recording and reproducing gaps so
their center lines lie parallel with one another. Misalignment of the gaps causes a loss
in output at short wavelengths.
