18WuD2x

entladungsstrahlen • epitaxial deposition 261
depending on the arc length. The term is derived
from the German word for discharge rays.
entrainment Providing a path for gases to escape
from an electrochemical cell or battery.
entrance delay In security applications, a delay
that allows authorized people time to leave the
protected area after activating the alarm system,
or to deactivate the system after entering the protected
area. The delay is approximately 30 to 45
seconds.
entropy 1. In all closed physical systems, the measure
of energy wasted. According to the second
law of thermodynamics, for example, supplied
heat can never be converted entirely into work.
2. In communications, the amount of information
in a message, defined as the base-10 logarithm of
the number of equivalent messages that can exist.
3. A natural process in which the energy in
the universe tends to become more uniformly distributed
with the passage of time.
entropy coding A form of digital encoding that
minimizes redundancy, thereby increasing the
amount of data in a given amount of memory or
storage space.
entry 1. A unit of computer input or output information.
2. A data item in a table or list. 3. A computer
source program statement. 4. In a computer
program, the address of the first instruction.
entry condition A condition that must be specified
before a computer program is run (e.g., establishing
operand values).
entry-level system 1. The least-sophisticated
computer that will perform the things that a user
requires. 2. A simple electronic or computer system
(e.g., an amateur radio transciever or personal
computer, intended for ease of operation,
and from which the user expects to upgrade to a
more powerful system at a later date).
entry point In a computer program, the first instruction
to be implemented, or a point during
the run when data can be entered.
envelope 1. On a graph, the imaginary line joining
successive signal peaks. In the graph for an amplitude-modulated
signal, the line reproduces the
modulating wave. 2. The enclosure of a transistor
or integrated circuit. 3. The glass shell of a vacuum
tube.
envelope delay In a tuned amplifier, time delay introduced
in the envelope of a modulated signal by
varying the phase of the envelope with the modulating
frequency. This delay varies directly with
the amount by which the sidebands shift, with respect
to the carrier frequency.
enveloped file A computer file with labels permitting
it to be handled by a computer of a type different
from that used to make the file.
environmental conditions See ENVIRONMENTAL
FACTORS.
environmental factors Aspects of the space immediately
surrounding and sometimes influencing
electronic equipment. Examples: altitude,
dust, light, moisture, noise, pressure, shock,
temperature, and vibration.
environmentally sealed Sealed against the effects
of adverse environmental factors.
environmental test chamber See CLIMATE
CHAMBER.
E o 1. Symbol for OUTPUT VOLTAGE. 2. Symbol for
zero reference voltage.
EOF Abbreviation of end of file.
EOL Abbreviation of end of line.
EOLM Abbreviation of electro-optical light modulator.
EOR Abbreviation of END OF (program) RUN.
EOS Abbreviation of electro-optical system(s).
EOT Abbreviation of end of tape.
EOTS Abbreviation of electro-optical tracking system.
E P 1. Symbol for PLATE VOLTAGE. 2. Symbol for
PEAK VOLTAGE.
EP Abbreviation for EXTENDED PLAY.
ephemeris time Time measured with respect to
the orbit of the earth around the sun. Initiated in
the year 1900 AD.
epipolar navigation A scheme for position sensing
and navigation that uses an artificially intelligent
vision system. Allows calculation of position and
velocity, based on changes in the visualized direction,
size, and shape of an object whose actual
location, size, and shape are precisely known. It
is used in some mobile robots.
episcotister A mechanical light beam modulator.
The device consists of a series of rotating disks
having transparent and opaque sections that alternately
interrupt and pass the light beam at an
audio-frequency rate.
Modulated
light
episcotister
Light
Stationary disk
Rotating
disk
epitaxial Pertaining to, or having the property of,
EPITAXY.
epitaxial deposition The tendency of certain materials
to grow on a semiconductor substrate under
certain conditions.