18WuD2x

EM • emissivity 255
EM 1. Abbreviation of EFFICIENCY MODULATION.
2. Abbreviation of ELECTROMAGNETIC(S). 3. Abbreviation
of electromagnetic iron. 4. Abbreviation
of ELECTROMAGNETIZER. 5. Abbreviation of
ELECTRON MICROSCOPE. 6. Abbreviation of EX-
POSURE METER. 7. Abbreviation of electromotive.
E m 1. Symbol for MAXIMUM VOLTAGE. 2. Symbol
for MAXIMUM JUNCTION FIELD.
emanation 1. Emission of electrons. 2. Emission
of radioactive particles or ionizing radiation. 3.
Emission of electromagnetic energy.
E max Symbol for MAXIMUM VOLTAGE.
embedded path A means of guiding a mobile robot
along a specific route. One common scheme uses
a buried, current-carrying wire that produces a
magnetic field. The robot can sense and follow
this field. Colored paints and tapes can also be
used in conjunction with machine vision systems.
Compare EDGE DETECTION.
embedded training The inclusion of training/
tutorial programs in computerized equipment
that assist users in the operation of the equipment.
embedding See ENCAPSULATION.
embossed-foil printed circuit A printed circuit
made by pressing the pattern from metal foil into
the insulating substrate and then removing the
surplus foil.
embossed-groove recording 1. A phonograph
record into which grooves are embossed, rather
than scribed. 2. Recording sound by embossing
grooves on record disks.
embossing stylus The rounded-tip stylus used to
make an embossed-groove recording.
EMC Abbreviation of ELECTROMAGNETIC COM-
PATIBILITY.
EME Abbreviation of earth-moon-earth. See MOON-
BOUNCE.
e/m e The ratio of the elementary electron charge to
its mass: 1.7588 × 10 11 coulombs per kilogram.
Also see CHARGE-MASS RATIO.
Emergency Broadcast System In the United
States, a general plan for dissemanating information
via broadcast stations in the event of a national
emergency.
emergency channel A communication channel allocated
for emergency service.
emergency communication Radio or other electronic
transmission and reception of urgent messages
(e.g., distress signals, storm warnings,
etc.).
emergency equipment 1. Apparatus kept in
standby status for immediate operation when
regularly used equipment fails. 2. Equipment, especially
vehicular, for use in emergency situations.
Examples are ambulances, fire-fighting
trucks and equipment, etc.
emergency power supply An alternating-current
(ac) or direct-current (dc) power unit kept in
standby status for immediate use when the regular
power supply fails.
emergency service A communications service devoted
exclusively to emergency communication.
EMF, emf Abbreviation of ELECTROMOTIVE
FORCE.
emf standard See STANDARD CELL.
EMG 1. Abbreviation of ELECTROMYOGRAM. 2.
Abbreviation of ELECTROMYOGRAPH.
EMI Abbreviation of ELECTROMAGNETIC INTER-
FERENCE.
E microscope See ELECTRON MICROSCOPE.
emission 1. The ejection of particles, especially
electrons, from a material. 2. Waves radiated
from any source (as from a transmitting antenna
or from an amplifier stage). 3. The emanation of
radiant, electromagnetic, acoustical, electrical, or
magnetic energy.
emission code A system of abbreviating the various
types of radio emission. See EMISSION MODE.
emission frequency 1. In communications, the
carrier frequency of the transmitted signal as it is
radiated from the antenna or fed into a transmission
line. 2. The actual frequency or frequency
range of a signal as it is transmitted or radiated.
This might be the carrier frequency. 3. The frequency
of energy in an emission band or bands in
a spectrum.
emission lines In a spectrum, radiation intensity
peaks that appear as bright lines in a visible display.
In a radio-frequency spectrum, the emission
lines occur as sharp peaks in radiated energy at
specific wavelengths.
emission mode Any of various official classifications
of radio communication emission types.
Emissions are designated according to the modulation
method used (e.g., continuous waves,
amplitude modulation, single-sideband with
suppressed carrier, frequency modulation, pulse
modulation, etc.).
emission power 1. The rate at which energy is radiated
from an object. 2. In radio communication,
the transmitter output power.
emission spectrum The radiation spectrum of a
substance that emits energy (e.g., the light spectrum
of an incandescent metal).
emission types See EMISSION MODE.
emission velocity The initial velocity of an electron
as it leaves an emitting surface.
emission wavelength 1. In communications, the
carrier wavelength of the transmitted signal as it
is radiated from the antenna or fed into a transmission
line. 2. The actual wavelength or wavelength
range of a signal as it is transmitted or
radiated. This might or might not be the carrier
wavelength. 3. The wavelength of energy in an
emission band or bands in a spectrum.
emissive power The rate at which a surface emits
energy of all wavelengths in all directions, per
unit area of radiating surface, regardless of temperature.
emissivity For a radiating source, the ratio
W 1 /W 2 , where W 1 is the energy emitted by the