I/O - Input/Output.
IC SYNCHROS - Obsolete synchros with reverse rotation and limited torque
capabilities .
IDEMPOTENT LAW - In Boolean algebra, combining a quantity with itself
either by logical addition or logical multiplication will result in a logical sum or
product that is the equivalent of the quantity (for example, A + A = A; A · A = A) .
IDENTITY LAW - In Boolean algebra, the law which states that any
expression is equal to itself (for example, A = A or A = A .
IDLER FREQUENCY - In a parametric amplifier, the difference between the
input signal and the pump signal frequency. Also called the LOWER-SIDEBAND FREQUENCY .
IF AMPLIFIER - Usually a narrow-bandwidth IF amplifier that is tuned to
one of the output frequencies produced by the mixer .
IGFET - Any field-effect transistor that has an insulated gate .
IMAGE FREQUENCY - An undesired frequency capable of producing the desired
frequency through heterodyning .
IMPEDANCE - The total opposition offered to the flow of an alternating
current. It may consist of any combination of resistance, inductive reactance, and
capacitive reactance. The symbol for impedance is Z .
IMPEDANCE ANGLE METER - A device that measures circuit impedance by
comparing the phase angle between voltage and current.
IMPLOSION - The inward bursting of a CRT because of high vacuum. The
opposite of explosion .
INCIDENT WAVE - (1) The wave that strikes the surface of a medium. (2) The
wave that travels from the sending end to the receiving end of a transmission line .
IN-CIRCUIT METER - A meter permanently installed in a circuit; used to
monitor circuit operation .
INCOHERENT - Refers to radiation on a broad band of frequencies .
INDEX OF REFRACTION - The degree of bending of an rf wave when passing
from one medium to another .
INDICATOR - Equipment in radar that provides a visual presentation of
target position information .
INDIRECTLY HEATED CATHODE - Same as the directly heated cathode with one
exception: The hot filament raises the temperature of the sleeve around the filament; the
sleeve then becomes the electron emitter .
INDUCED-CHANNEL MOSFET - A MOSFET in which there is no actual channel
between the source and the drain. This MOSFET is constructed by making the channel of the
same type of material as the substrate .
INDUCED CHARGE - An electrostatic charge produced on an object by the
electric field that surrounds a nearby object .
INDUCED CURRENT - Current caused by the relative motion between a
conductor and a magnetic field .
INDUCED ELECTROMOTIVE FORCE - The electromotive force induced in a
conductor because of the relative motion between the conductor and a magnetic field .
INDUCED VOLTAGE - See INDUCED ELECTROMOTIVE FORCE .
INDUCTANCE - The property of a circuit that tends to oppose a change in
the existing current flow. The symbol for inductance is L .
INDUCTANCE BRIDGE - An ac bridge circuit used to measure an unknown value
of inductance .
INDUCTION - The act or process of producing voltage and current by the
relative motion of a magnetic field across a conductor .
INDUCTION FIELD - The electromagnetic field that is produced about an
antenna when current and voltage are present on the same antenna .
INDUCTION LOSSES - The losses that occur when the electromagnetic field
around a conductor cuts through nearby metallic objects and induces a current into that
object .
INDUCTION MOTOR - A simple, rugged, ac motor with desirable
characteristics. The rotor is energized by transformer action (induction) from the stator.
Induction motors are used more than any other type .
INDUCTIVE COUPLING - Coupling of two coils by means of magnetic lines of
force. In transformers, coupling applied through magnetic lines of force between the
primary and secondary windings .
INDUCTIVE REACTANCE - The opposition to the flow of an alternating current
caused by the inductance of a circuit, expressed in ohms. Identified by the symbol XL .
INERTIA - The physical tendency of a body in motion to remain in motion
and a body at rest to remain at rest unless acted upon by an outside force (Newton's First
Law of Motion) .
INFINITE - (1) Extending indefinitely, endless. (2) Boundless, having no
limits. (3) An incalculable number .
INFRALOW FREQUENCY - The band of frequencies from 300 Hz to 3,000 Hz [19].
INFRASONIC (SUBSONIC) - Sounds below 15 hertz .
IN PHASE - Applied to the condition that exists when two waves of the same
frequency pass through their maximum and minimum values of like polarity at the same
instant .
INPUT - (1)The current, voltage, power, or driving force applied to a
circuit or device .(2)The data entered into a computer system for processing.
INPUT DEVICES - Devices for reading data and programs into the computer
system for processing.
INPUT END - The end of a two-wire transmission line that is connected to a
source .
INPUT IMPEDANCE - Impedance presented to the transmitter by the
transmission line and its load .
INPUT/OUTPUT - Pertaining to either input or output or both, especially in
data processors .
INPUT/OUTPUT DEVICES - Secondary storage devices for writing and reading
data. Magnetic tape drives, magnetic disk drives, and drums are examples.
INSERTION LOSS - The difference between the amount of power applied to a
load before and after the insertion of a device in the line.
INSTANTANEOUS AMPLITUDE - The amplitude at any given point along a sine
wave at a specific instant in time .
INSTANTANEOUS AUTOMATIC GAIN CONTROL (IAGC) - A circuit that can vary the
gain of the radar receiver with each input pulse to maintain a nearly constant output peak
amplitude .
INSTANTANEOUS VALUE - The magnitude at any particular instant when a value
is continually varying with respect to time .
INSULATION - A material used to prevent the leakage of electricity from a
conductor and to provide mechanical spacing or support as protection against accidential
contact with the conductor .
INSULATION RESISTANCE - The resistance offered by an insulating material
to current leakage .
INSULATOR - (1) Material of such low conductivity that the flow of current
through it can usually be neglected. (2) A device having high electrical resistance; used
for supporting or separating conductors so as to prevent undesired flow of current from
the conductors to other objects .
INTEGRATED CIRCUIT (IC) - (1) A circuit in which many elements are
fabricated and interconnected by a single process (into a single chip), as opposed to a
"nonintegrated" circuit in which the transistors, diodes, resistors, and other
components are fabricated separately and then assembled . (2) Elements inseparably
associated and formed on or within a single substrate .
INTELLIGENCE - In communications any signal that conveys information
(voice, teletypewriter, facsimile) .
INTENSITY (OF SOUND) - The measurement of the amplitude of sound energy.
Generally synonymous with loudness .
INTERACTION SPACE - The region in an electron tube where the electrons
interact with an alternating electromagnetic field .
INTERCEPT - The point where two lines drawn on a graph cross each other .
INTERELECTRODE CAPACITANCE - The capacitance between the electrodes of an
electron tube .
INTERFERENCE - Any disturbance that produces an undesirable response or
degrades a signal .
INTERLAYER TRANSFER - Any loose material, such as oxide, generated by tape
wear or a head-stick condition which is transferred from the oxide to the back of the
tape, or from the back side to the oxide when the tape is wound on a reel.
INTERMEDIATE FREQUENCY (IF) - A lower frequency to which an rf echo is
converted for ease of amplification .
INTERMEDIATE-LEVEL MAINTENANCE (SM&R Code I) - Direct support and
technical assistance to user organizations. Tenders and shore-based repair facilities .
INTERMEDIATE POWER AMPLIFIER - The amplifier between the oscillator and
final power amplifier .
INTERMODULATION DISTORTION - (1) A signal non-linearity with frequencies
in the output equal to sums and differences of integral multiples of the component
frequencies present in the input signal. (2) Harmonies are usually not included as part of
the intermodulation distortion.
INTERNAL STORAGE (MEMORY) - See storage, primary.
INTERPOLES - Small auxiliary poles, placed between main field poles, whose
magnetic field opposes the armature field and cancels armature reaction. Interpoles
accomplish the same thing as compensating windings .
INTERRECORD/INTERBLOCK GAP - A blank section of recording surface
separating each record or block of records on a magnetic data medium.
INTERSECTION LAW - In Boolean algebra, the law which states that if one
input to an AND gate is already TRUE, then the output will depend upon the state of the
other inputs only .
INVERSELY - Inverted or reversed in position or relationship .
INTERSYMBOL INTERFERENCE - (1) An interference resulting in a phase shift
of the cell playback crossover point with respect to the data clock. (2) When a recording
system has limited record resolution, a flux transition being recorded will extend beyond
its cell boundaries, adding or subtracting from the flux in the adjacent bit cells of
symbols.
INVERT - To change a physical or logical state to its opposite state .
INVERTER - A circuit with one input and one output. Its function is to
invert or reverse the input. When the input is high, the output is low, and vice versa.
The inverter is sometimes called a NOT circuit, since it produces the reverse of the input
.
ION - An electrically charged atom or group of atoms. Negative ions have
an excess of electrons; positive ions have a deficiency of electrons .
IONIZATION - (1) The process of producing ions. (2) The electrically
charged particles produced by high-energy radiation, such as light or ultraviolet rays, or
by the collision of particles during thermal agitation .
IONIZATION POINT - The potential required to ionize the gas of a
gas-filled tube. Sometimes called firing potential .
IONIZE - To make an atom or molecule of an element lose an electron, as by
X-ray bombardment, and thus be converted into a positive ion. The free electron may attach
itself to a neutral atom or molecule to form a negative ion .
IONOSPHERE - The most important region of the atmosphere extending from 31
miles to 250 miles above sea level. Contains four cloud-like layers that affect radio
waves .
IONOSPHERIC STORMS - Disturbances in the earth's magnetic field that make
communications practical only at lower frequencies .
IRIS - A metal plate with an opening through which electromagnetic waves
may pass. Used as an impedance-matching device in waveguides .
IRON OXIDE - (See gamma-ferric oxide.)
I2R LOSS - See COPPER LOSSES .
ISOLATION - The prevention of unwanted interaction or leakage between
components .
ISOMETRIC DIAGRAM - A diagram showing the outline of a ship, aircraft, or
equipment and the location of equipment and cable runs .
ISOTROPIC RADIATION - The radiation of energy equally in all directions .
