Electrical Engineering Dictionary - part 62

(2) a device, consisting of a micropro-

cessor, firmware (often in EPROM), and/or
FPGAs/EPLDs, which is dedicated to spe-
cific functions, and becomes an inseparable
component of a device or system, in contrast
to devices that are controlled by stand-alone
computers. Embedded computers use em-
bedded software, which integrates an oper-
ating system with specific drivers and ap-
plication software. Their design often re-
quires special software–hardware codesign
methods for speed, low power, low cost, high
testability or other special requirements.

(3) software that is part of a larger system

and performs some of the requirements of
that system; e.g., software used in an aircraft
or rapid transit system. Such software does
not provide an interface with the user. See

firmware

embedded computer system

See

embed-

ded computer

embedded system

embedded passives

3-D packaging so-

lution, consisting of embedding passive el-
ements into the mounting substrate, for in-
creasing the packaging efficiency.

embedded system

software that is part

of a larger system and performs some of the
requirements of that system; e.g., software
used in an aircraft or rapid transit system.
Such software does not provide an interface
with the user. See also

firmware

EMC

See

electromagnetic compatibility

EMI

See

electromagnetic interference

EMI filter

See

electromagnetic interfer-

ence filter

emission credit

a scheme in the USA for

the control of nitrous oxide and sulfur diox-
ide emissions from industrial plants. A utility
can purchase from the government the right
to emit a certain quantity of pollutant. If it
does not emit this amount, the credit can be
sold on the market to another plant which

may need to emit some pollutant. The resale
value of the pollution credit forms a finan-
cial incentive for a facility to emit as little
pollution as possible.

emissivity

the fraction of the power in-

cident on a material that is reradiated after
being absorbed by the material. For a mate-
rial in thermal equilibrium, the emissivity is
equal to the absorptivity.

emitter follower

See

common collector

amplifier

emitter-coupled logic (ECL)

a very high

speed bipolar transistor logic circuit family.

emitter-coupled pair

See

differential

pair

EMP

See

electromagnetic pulse

empirical distribution function

See

histogram

empirical model

mathematical model

based on curve-fitting specific mathematical
functions to measured data, rather than on
device physics. Empirical models generally
have a low to midrange modeling valuation
coefficient.

EMTP

the Electro-Magnetic Transient

Program, a computer program which simu-
lates an electric power system such that its
response to disturbances may be accurately
predicted.

emulate

executing a program compiled to

one instruction set on a microprocessor that
uses an incompatible instruction set, by trans-
lating the incompatible instructions while the
program is running.

emulation

a model that accepts the same

inputs and produces the same outputs as a
given system. To imitate one system with
another. Contrast with

simulation

2000 by CRC Press LLC

emulation mode

state describing the time

during which a microprocessor is performing
emulation.

emulator

(1) the firmware that simulates

a given machine architecture.

(2) a device, computer program, or system

that accepts the same inputs and produces the
same outputs as a given system. Compare
with

simulator

EMV

See

electromagnetic vulnerability

encapsulation

property of a program that

describes the complete integration of data
with legal process relating to the data.

enclosure

a box, cabinet, wall, fence,

barrier, or other means designed to protect
personnel from accidentally contacting ener-
gized electrical parts and to protect the elec-
trical parts from physical damage.

encoder

(1) a device that directly creates

a digital signal based on an analog value.

(2) a logic circuit with 2

inputs and

outputs, the outputs indicating the number of
the one input line that is asserted.

(3) a device used to obtain positional in-

formation. The encoder uses a disk mounted
on the shaft of a rotating machine and a light
source.

The combination provides lights

pulses that can be decoded to provide the an-
gular position of the motor. See also

absolute

encoder

and

incremental encoder

encoding

(1) the act of placing informa-

tion to be transmitted in a form that can be
transmitted over a particular medium and will
be recognizable by the receiver. See also

coding

(2) in computing systems, to represent

various pieces of information by a defined
sequence of the binary digits 0 and 1, called
bits. To apply the rules of a code.

encryption

the transformation employed

to transform information to be transmitted
(plaintext) into a format that is unintelligible

(ciphertext or a cryptogram). The ciphertext
can then be transmitted via a communication
channel without revealing the contents of the
plaintext. This is achieved by means of an
encryption key. A system for performing en-
cryption is also known as a cipher. The infor-
mation to be encrypted is referred to as plain-
text, and the encrypted message resulting
from encryption is referred to as ciphertext.
The intended receiver of the ciphertext also
has the encryption key, and by having both
the ciphertext and the encryption key avail-
able, the original plaintext can be recovered.
See also

public key cryptography

private key

cryptography

encryption key

a codeword used for de-

cryption of ciphertext into plaintext in en-
cryption systems.

Ciphertext can then be

transmitted via a communication channel
without revealing the contents of the plain-
text. The plaintext can only be recovered by
someone in possession of the encryption key.
See also

end bell

the cap that forms the end of the

stator housing for an electric machine with a
cylindrical frame.

end-around carry

technique used in

one’s complement arithmetic, in which a car-
ryover of the result of an addition or sub-
traction beyond the leftmost bit during addi-
tion (or subtraction) is “wrapped around” and
added to the result.

end-effector

a part found at the free

end of the chain of the links which form
a manipulator. Position and orientation of
the manipulator are referred to the end-
effector. The frame attached the end-effector
is known as end-effector frame. The end-
effector can be a gripper or it can be at-
tached to the end-effector. The orthonormal
end-effector frame consists of three unit vec-
tors

a-approach (it approaches the object) o-

orientation (which is normal to the sliding

2000 by CRC Press LLC

plane between the fingers of the gripper),
and

n-normal vector to two others so that the

frame (

n, o, a) is right-handed.

end-fire

the pattern factor is maximum in

the

E plane (for a dipole antenna along the

z axis, this is the plane where θ = 0 or 180
degrees).

end-fire array

a linear phased array an-

tenna in which the amplitudes and phases of
the element excitations are adjusted such that
the direction of maximum radiation is along
the axis passing through the center of the ar-
ray elements.

endian

an adjective used with a qualifier

to indicate how long values are constructed
from smaller values that reside in memory. A
“big-endian” machine constructs long values
by placing the smaller parts from the lower
addresses at the left end of the value (the
“big” end).

endoscope

remote imaging system used

by physicians to examine a patient’s internal
organs. The cylindrical rod is placed either
through an existing opening in the body or
through a small incision. The rod contains an
illuminating fiber optic bundle and an optical
system to deliver the image to a video mon-
itor. In a conventional endoscope, the image
is transmitted through a series of lenses to
a camera outside of the patient. In an elec-
tronic endoscope the image is collected by a
CCD camera positioned inside the patient.

endpoint detection

the process of iso-

lating spoken words, typically used subse-
quently for word recognition.

ends

a crimped-type wire connector.

energy

that which does work or is capa-

ble of doing work. In electrical systems, it
is generally a reference to electrical energy
measured in kilo-watt hours.

energy band

continuous interval of en-

ergy levels that are allowed in the periodic
potential field of the crystalline lattice.

energy banking

pertaining to the mainte-

nance of a thermal unit on hot reserve.

energy compaction

in a transformation,

the concentration of the input signal energy
into a relatively small part of the transformed
signal. A linear transform of a random vector
compacts the signal energy when the energy
or variance of a small number of transform
coefficients is large relative to the variance of
the other coefficients.

energy conservation

the conservation of

energy between the input and output of a sys-
tem; i.e., the energy of the output signal is
equal to that of the input signal to within
a constant factor. A unitary or orthogonal
transform conserves energy in that the energy
or magnitude of the output vector is equal to
that of the input vector.

energy gap

the width of the energy inter-

val between the top of the valence band and
the bottom of the conduction band.

energy level

one of the specific values

possible for the energy of an electron in an
atom or molecule.

energy product

the product of the mag-

netic flux density,

B and magnetic field inten-

sity,

H at any operating point on the normal

demagnetization curve, indicating the energy
delivered by the magnet. The maximum en-
ergy product is commonly used to designate
varying grades of materials.

energy relaxation time

the characteristic

time for energy loss to scattering processes.

energy signal

a continuous time signal

f (t) is an energy signal if

∞

−∞

f (t)

dt < ∞ .

2000 by CRC Press LLC

For example, the signal

f (t) = e

−t

, t ≥ 0 is

an energy signal. The signal

f (t) = 1 is not

an energy signal. The definition has practi-
cal significance if the signal

f is a voltage,

or current, applied to an electric circuit, as
shown in the figure. The energy dissipated
by the circuit is given by

inf ty

−∞

v(t)

dt .

A discrete time signal is an energy signal

∞

k=−∞

f (k)

< ∞ .

energy-density spectrum

for a continu-

ous time signal

x(t) the function |X(w)|

where

X(w) is the Fourier Transform of

The function

|X(w)|

is referred

to as an energy-density spectrum because
1|X(w

is proportional to the energy in

the signal

x in a bandwidth 1 around the

frequency

. Analogously, a discrete time

signal

x[n] has an energy-density spectrum

|X()|

enhanced backscattering

peak of the an-

gular distribution of scattered intensity in the
retroreflection direction, due to multiple scat-
tering of light in dense volumes or very rough
boundaries.

enhanced graphics adaptor (EGA)

video adapter proposed by IBM in 1984. It is
capable of emulating CGA and MDA. It can
reach 43 lines with 80 columns. In graphic
mode, it can reach 640

× 350 pixels (wide per

high) with 16 colors selected from a pallet of
64.

enhanced small device interface

See

enhanced small disk interface

enhanced small disk interface (ESDI)
mass storage device interface similar to MFM
and RLL except that the clock recovery cir-
cuits are in the peripheral device rather than

in the controller.

Originally designed by

Maxtor.

enhancement

improvement of signal

quality without reference to a model of sig-
nal degradation.

See

restoration

image

enhancement

enhancement mode

an FET that is off

when zero volts bias is applied from gate to
source.

ENI

See

equivalent noise current

ENR

See

excess noise ratio

enriched uranium

uranium which con-

tains 1.5% to 5% of fissile U-235 and is thus
suitable for use in power reactors.

enrichment

the process of increasing the

ratio of one isotope of a chemical element,
e.g. fissile uranium, to another, less desirable
isotope, e.g. non-fissile uranium.

ensemble processor

a parallel processor

consisting of a number of processing ele-
ments, memory modules, and input/output
devices under a single control unit. It has
no interconnection network to provide inter-
processor or processor-memory communica-
tions.

entity

a software process that implements

a part of a protocol in a computer communi-
cation network.

entity relationship diagram

a diagram

that describes the important entities in a sys-
tem and the ways in which they are interre-
lated.

entropy

information theoretic quantity

representing the amount of uncertainty in
guessing the value of a random variable. For
a discrete random variable

X, with probabil-

ity mass function

p(x) defined on the support

2000 by CRC Press LLC

Content .. 60 61 62 63 ..