Page 66 - Electrical Engineering Dictionary

attenuated total reflection the phe- the form
nomenon associated with the appearance of a
n
reflection minimum identified with the gen- a j : U →{−1, 0, 1} .
eration of surface waves at the metal — air
interface in a prism, air, metal arrangement.
attribute set a set of vectors (signals)
attenuation the exponential decrease lying in metric space that possess prescribed
with distance, in the amplitude of an elec- properties.
tric signal traveling along a very long trans-
mission line due to losses in the support- audio science of processing signals that
ing medium. In electromagnetic systems at- are within the frequency range of hearing,
tenuation is due to conductor and dielectric that is, roughly between 20 hertz and 20 kilo-
losses. In fiber optic systems attenuation hertz. Also, name for this kind of signal.
arises from intrinsic material properties (ab-
sorption and Rayleigh scattering) and from audio channels the portion of the cir-
waveguide properties such as bending, mi- cuit containing frequencies that correspond
crobending, splices, and connectors. to the audible sound waves. Audio frequen-
cies range from approximately 15 hertz to
attenuation coefficient See absorption 20,000 hertz.
coefficient.
audio coding the process of compress-
attenuation constant the real part of the ing an audio signal for storage on a digital
complex propagation constant for an electro- computer or transmission over a digital com-
magnetic wave. munication channel.

attenuator a device or network that ab- audio follow-video switcher (AFV) a
sorbs part of a signal while passing the re- switcher that simultaneously switches the
mainder with minimal distortion. video and audio information. The term is
associated with the action of the audio signal
attractor an asymptotic state of a dy- and corresponding video signal switching to-
namical system of which there are three basic gether.
types. Either (i) the system comes to rest and
the attractor is a fixed point in state space, augmented code a code constructed from
(ii) the system settles into a periodic motion another code by adding one or more code-
known as a limit cycle, or (iii) the system words to the original code.
enters a chaotic motion, in which case the
attractor is called strange. aural subcarrier in a composite tele-
vision signal, the frequency division multi-
attribute a special function in Pawlak’s plexed carrier placed outside the visual pass-
information system. Pawlak’s information band that carries the audio modulation. In
system S is a pair (U, A) where the set U is the NTSC (United States) system, it is placed
called the universe and has n members de- 4.5 Mhz higher than the visual carrier.
noted x i , while the set A consists on m func-
tion on the universe U. These functions are auto-regressive moving-average model
called the attributes and denoted a j . The at- (ARMA) the discrete-time input–output
tributes are vector-valued functions that may model in which the current output depends
be interpreted, for example, as issues under both on its past values (auto-regressive part)
negotiation by the members of the universe and the present and/or past values of the input
U. An example of an attribute is a function of (moving-average part).

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2000 by CRC Press LLC