EBCDIC (Extended Binary Coded Decimal Interchange Code) - An 8-bit coding
system for representing uppercase and lowercase letters, numbers, and special characters.
ECHO - (1) The reflection of the original sound wave as it bounces off a
distant surface . (2) The rf signal reflected back from a radar target .
ECHO BOX - A resonant cavity device that is used to check the overall
performance of a radar system. It receives a portion of the transmitted pulse and
retransmits it back to the receiver as a slowly decaying transient .
ECLIPSE - A condition in which the satellite is not in view or in direct
line of sight with the sun. This happens when the earth is between them .
EDDY CURRENT - Induced circulating currents in a conducting material that
are caused by a varying magnetic field .
EDDY CURRENT LOSS - Losses caused by random current flowing in the core of
a transformer. Power is lost in the form of heat .
EDISON EFFECT - Also called RICHARDSON EFFECT. The phenomenon wherein
electrons emitted from a heated element within a vacuum tube will flow to a second element
that is connected to a positive potential .
EFFECTIVE VALUE - Same as ROOT-MEAN-SQUARE .
EFFICIENCY - The ratio of output-signal power compared to the total input
power, generally expressed as a percentage .
E-FIELD - Electric field that exists when a difference in electrical
potential causes a stress in the dielectric between two points .
ELASTICITY - The ability of a substance to return to its original state .
ELECTRIC CURRENT - The flow of electrons .
ELECTRIC (E) FIELD - The field of force that is produced as a result of a
voltage charge on a conductor or antenna .
ELECTRICAL CHARGE - Symbol Q, q. Electric energy stored on or in an
object. The negative charge is caused by an excess of electrons; the positive charge is
caused by a deficiency of electrons .
ELECTRICAL CHEMICAL - The action of converting chemical energy into
electrical energy .
ELECTRICAL-LOCK - A synchro zeroing method. This method is used only when
the rotors of the synchros to be zeroed are free to turn and their leads are accessible .
ELECTRICAL POWER SYSTEM - Provides the necessary input power .
ELECTRICAL SYMBOLS - Graphic symbols used to illustrate the various
electrical or electronic components of a circuit .
ELECTRICAL ZERO - A standard synchro position, with a definite set of
stator voltages, that is used as the reference point for alignment of all synchro units .
ELECTRODE - The terminal at which electricity passes from one medium into
another, such as in an electrical cell where the current leaves or returns to the
electrolyte .
ELECTRODYNAMIC METER MOVEMENT - A meter movement using fixed field coils
and a moving coil; usually used in ammeters and wattmeters .
ELECTRODYNAMOMETER - A meter using an electrodynamic movement to measure
an electric current .
ELECTROLYSIS - The process of changing the chemical composition of a
material by passing an electric current through it .
ELECTROLYTE - A solution of a substance that is capable of conducting
electricity. An electrolyte may be in the form of either a liquid or a paste .
ELECTROMAGNET - An electrically excited magnet capable of exerting
mechanical force or of performing mechanical work .
ELECTROMAGNETIC - The term describing the relationship between electricity
and magnetism. A quality that combines both magnetic and electric properties .
ELECTROMAGNETIC FIELD - The combination of an electric (E) field and a
magnetic (H) field .
ELECTROMAGNETIC INDUCTION - The production of a voltage in a coil because
of a change in the number of magnetic lines of force (flux linkages) passing through the
coil .
ELECTROMAGNETIC INTERFERENCE - Man-made or natural interference that
degrades the quality of reception of radio waves .
ELECTROMAGNETIC RADIATION - The radiation of radio waves into space .
ELECTROMAGNETISM - The generation of a magnetic field around a
current-carrying conductor .
ELECTROMOTIVE FORCE (emf) - The force (voltage) that produces an electric
current in a circuit .
ELECTRON - The elementary negative charge that revolves around the nucleus
of an atom .
ELECTRON GUN - An electrode of a CRT that is equivalent to the cathode and
control grid of conventional tubes. The electron gun produces a highly concentrated stream
of electrons .
ELECTRON ORBITAL MOVEMENT - The movement of an electron around the nucleus
of an atom .
ELECTRON SHELL - A group of electrons which have a common energy level
that forms part of the outer structure (shell) of an atom .
ELECTRONIC COUNTER-COUNTERMEASURES (ECCM) CIRCUITS - See ANTIJAMMING
CIRCUITS .
ELECTRONIC-EQUIPMENT DEHYDRATOR - A device that provides an alternate
dry-air input in the event of failure of the central dry-air system. It may include a
compressor .
ELECTRONIC FREQUENCY COUNTER - An instrument that counts the number of
cycles (pulses) occurring during a precise time interval .
ELECTRONIC SCANNING - Scanning in which the axis of the beam is moved,
relative to the antenna axis, in a desired pattern .
ELECTRONIC SWITCH - A circuit that causes a start-and-stop switching
action by electronic means .
ELECTRONICS DRY-AIR BRANCH - A common line for providing dry air to
various electronic equipment, such as search radar, fire-control radar, and repeaters .
ELECTRONIC TUNING - In a reflex klystron, changing the frequency and
output power of the tube by altering the repeller voltage .
ELECTRON SPIN - The movement of an electron around its axis .
ELECTROSTATIC - Pertaining to electricity at rest, such as charges on an
object (static electricity) .
ELECTROSTATIC DEFLECTION - The method of deflecting an electron beam by
passing it between parallel charged plates mounted inside a cathode-ray tube .
ELECTROSTATIC-DISCHARGE SENSITIVE (ESDS) DEVICE - Electronic components
that are susceptible to damage from static charges.
ELECTROSTATIC FIELD - The field of influence between two differently
charged bodies .
ELECTROSTATIC METER MOVEMENT - A meter movement that uses the
electrostatic repulsion of two sets of charged plates (one fixed and the other movable).
This meter movement reacts to voltage rather than to current and is used to measure high
voltage .
ELECTROSTATIC STRESS - The force exerted on an insulator by the voltage in
a conductor .
ELEMENT - (1) A substance, in chemistry, that cannot be divided into
simpler substances by any means ordinarily available . (2) A part of an antenna that can
be either an active radiator or a parasitic radiator .
ELEPHANT TRUNK - Ducting used for ventilation purposes .
ELEVATION ANGLE - The angle between the horizontal plane and the line of
sight to a target or object .
EMERGENCY POWER - Temporary source of limited electrical power used upon
the loss of the normal power source .
EMF (ELECTROMOTIVE FORCE) - The force that causes electricity to flow
between two points with different electrical charges or when there is a difference of
potential between the two points. The unit of measurement is volts .
EMITTER - The element in a transistor that emits current carriers
(electrons or holes) .
EMITTER-INJECTION MODULATOR - The transistor equivalent of the cathode
modulator. The gain is varied by changing the voltage on the emitter .
ENAMEL - A synthetic compound of cellulose acetate (wood pulp and
magnesium). Used to insulate wire in meters, relays, and motor windings .
ENCAPSULATED - Imbedded in solid material or enclosed in glass or metal .
END-FEED METHOD - A method in which one end of an antenna is connected
through a capacitor to the final output stage of a transmitter .
END-FIRE ARRAY - An array in which the direction of radiation is parallel
to the axis of the array .
ENERGY - The ability or capacity to do work .
EPHEMERIS - A table showing the precalculated position of a satellite at
any given time .
Ep-Ip CURVE - The characteristic curve of an electron tube used to
graphically depict the relationship between plate voltage (Ep) and plate current (I p) .
EPITAXIAL PROCESS - A method of depositing a thin, uniformly doped
crystalline region (layer) on a substrate .
EPROM - The acronym for erasable programmable read-only memory.
EQUATORIAL ORBIT - An orbit that occurs when the plane of a satellite
coincides with the plane of the earth at the equator .
EQUIPMENT NOISE - (See noise.)
EQUIVALENT RESISTANCE (Req) - A resistance that represents the total ohmic
values of a circuit component or group of circuit components. Usually drawn as a single
resistor in a simplified circuit .
ERASURE - A process by which a signal recorded on a tape is removed and
the tape made ready for rerecording. May be accomplished in two ways. (1) In ac erasure,
the tape is demagnetized by an alternating magnetic field that is reduced in amplitude
from an initially high value. May be accomplished by passing the tape over an erase head
fed with high-frequency ac, or by placing the whole roll of tape in a decreasing ac field
(bulk erasure). (2) In dc erasure, the tape is saturated by applying a primarily
unidirectional field. May be accomplished by passing the tape over a head fed with dc or
over a permanent magnet. Additional stages may be included in dc erasure to leave the tape
in a more nearly unmagnetized condition.
ERECTING (A GYRO) - The positioning of a gyro into a desired position and
the maintaining of that position .
ERROR DETECTOR - The component in a servosystem that determines when the
load has deviated from its ordered position, velocity, and so forth .
ERROR REDUCER - The name commonly given to the servomotor in a
servosystem. So named because it reduces the error signal by providing feedback to the
error detector .
ERROR SIGNAL - (1) In servosystems, the signal whose amplitude and
polarity or phase are used to correct the alignment between the controlling and the
controlled elements. (2) The name given to the electrical output of a control transformer
.
E-TRANSFORMER - A special form of differential transformer employing an
E-shaped core. The secondaries of the transformer are wound on the outer legs of the E,
and the primary is wound on the center leg. An output voltage is developed across the
secondary coils when its armature is displaced from its neutral position. This device is
used as an error detector in servosystems that have limited load movements .
E-TYPE T-JUNCTION - A waveguide junction in which the junction arm extends
from the main waveguide in the same direction as the E-field in the waveguide .
EUTECTIC ALLOY - An alloy that changes directly from a solid to a liquid
with no plastic or semiliquid state .
EUTECTIC SOLDER - An alloy of 63 percent tin and 37 percent lead. Melts at
361°F .
EXCITATION VOLTAGE - The supply voltage required to activate a circuit .
EXCITING CURRENT - The current that flows in the primary winding of a
transformer when the secondary is open-circuited; it produces a magnetic flux field. Also
called magnetizing current .
EXCLUSIVE OR - A function whose output is a 1 if one and only one of the
input variables is a 1 .
EXCLUSIVE-OR GATE - A gate that produces a logic 1 output when the inputs
are different, but not when they are the same .
EXPONENT - The numeral written in superscript (102 ) which indicates the
power to which the base is to be raised .
EXPRESSION - A validated series of variables, constants, and functions
that can be connected by operating symbols to describe a desired computation .
EXTERNALLY EXCITED METER - A term used to describe meters that get their
power from the circuit to which they are connected .
EXTERNALLY SYNCHRONIZED RADAR - A radar system in which timing pulses are
generated by a master oscillator external to the transmitter .
EXTREMELY HIGH FREQUENCY - The band of frequencies from 30 gigahertz to
300 gigahertz .
EXTREMELY LOW FREQUENCY - The band of frequencies up to 300 hertz .
EXTRINSIC - A semiconductor in which impurities have been added to create
certain charge carrier concentrations .
