Page 121 - Electrical Engineering Dictionary

formation symbol and not visiting the zero CATV Seecommunity-antennatelevision.
state. After decoding, a finite number of
(channel) errors can result in an infinite num-
ber of errors (catastrophic error propagation). Cauchy distribution the density function
for a Cauchy distributed random variable X
catastrophic error propagation when is
1
the state diagram contains a zero distance f X (x) = 2
path from some nonzero state back to the 1 + x
same state, the transmission of a 1 causes Note that the moments for this random vari-
an infinite number of errors. See also able do not exist, and that the cumulative dis-
catastrophic encoder. tribution function is not defined. See also
probability density function, moment.
catastrophic thermal failure an immedi-
ate, thermally induced total loss of electronic Caurer filter See elliptic filter.
function by a component or system.
causal system a system whose output
does not depend on future input; the output
catcher a cavity resonator of a multi-
at time t may depend only on the input sig-
cavity klystron proximate to the collector to
nal {f(τ) : τ ≤ t}. For example, the volt-
catch microwave energy from the bunched
age measured across a particular element in a
electrons.
passive electric circuit does not depend upon
future inputs applied to the circuit, and hence
categoric input a nonnumeric (symbolic) is a causal system.
input, e.g., gender, color, which is usually fed
If a system is not causal, then it is non-
to a network using one-out-of-N coding.
causal. An ideal filter which will filter in real
time all frequencies present in a signal f(t)
catenation symbols strung together to requires knowledge of {f(τ) : τ> t}, and is
form a larger sequence, as the characters in a an example of a noncausal system.
word and the digits in a number.
causality a system H : X e → X e ,or
cathode the negative electrode of a de- equivalently, an operator that maps inputs
vice. Contrast with anode. from the extended space X e into outputs from
the same space where the output at time t
is not a function of future inputs. This can
cathode ray tube (CRT) a vacuum tube
be expressed using truncations as follows: A
using cathode rays to generate a picture on a
system H is causal if
fluorescent screen. These cathode rays are in
fact the electron beam deflected and modu-
[Hx(·)] T = [Hx T (·)] T ∀x ∈ X e
lated, which impinges on a phosphor screen
to generate a picture according to a repeti-
See also extended space and truncation.
tive pattern refreshed at a frequency usually
between 25 and 72 Hz.
cavity (1) a fully enclosed, hollow con-
ductor, in which only time-harmonic electro-
cathodoluminescent the property of lu- magnetic fields of specific frequencies (i.e.,
minescent crystals (phosphors) to emit visi- resonant frequencies) exist. Each resonant
ble light with bombarded electrons. frequency is identified by a collection of
numbers in conjunction with a mode designa-
catoptric an optical system made up of tor of the transverse electric, transverse mag-
only reflective elements (mirrors). netic, or transverse electromagnetic type.

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2000 by CRC Press LLC