Page 153 - Electrical Engineering Dictionary

bits before transmission. The inverse loga- partments are described by the first-order dif-
rithmic function is used to expand the code ferential or difference equations, and in this
to its original number of bits before convert- sense they form a system of state equations.
ing it into an analog signal. Typically used Although the most popular application of
in telecommunications systems to minimize compartmental models is in modeling pop-
bandwidth without degrading low-amplitude ulation dynamics and other biomedical phe-
signals. nomena, they may be also used to describe
some engineering processes, e.g., distillation
companding a process designed to min- columns. The case of linear time-invariant
imize the transmission bit rate of a signal by compartments in which exchange rates are
compressing it prior to transmission and ex- proportional to the state of the donor com-
panding it upon reception. It is a rudimen- partments may be treated by Laplace trans-
tary data compression technique that requires forms and transfer function analysis.
minimal processing.
compatibility (1) two different imple-
companion matrix the coefficient ma-
mentations of the same component whereby
trix in the state-equation representation of the
they may both be used in a system with no
network describable by a linear differential
modification(oftenusedinthecontextofnew
equation.
microprocessors running software compiled
for older microprocessors).
comparator (1) a logic element that com-
(2) the capability of a functional unit to
pares two binary numbers (A and B)tode-
meet the requirements of a specified inter-
termine if A = B, A<B,or A>B.An
face.
exclusiveNORgateoperateslikea1-bitcom-
parator.
(2)asoftwaretoolthatcomparestwocom- compensated pulsed alternator (CPA)
puter programs, files, or sets of data to iden- See compulsator.
tify commonalities or differences. Typical
objects of comparison are similar versions of compensating winding a winding found
source code, object code, data base files, or in DC machines that is placed in the faces
test results. of the main field poles, and connected in se-
ries with the armature winding, to produce
compare instruction an instruction used an mmf equal and opposite to the mmf of
to compare two values. The processor flags the armature, thereby reducing the effect of
are updated as a result. For example, the in-
armature reaction.
struction CMP AL,7 compares the contents
of register AL with 7. The zero flag is set if
compensation (1) operations employed
AL equals 7. An internal subtraction is used
in a control scheme to counteract dynamic
to perform the comparison.
lags or to modify the transformation between
measured variables and controller output to
compartmental model a dynamical
produce prompt stable response.
model used in analysis of biomedical, phar-
macokinetic, and ecological systems. The (2) the alteration of the dynamic behav-
main idea in compartmental modeling is to ior of a process by the addition of sys-
“lump” in reality distributed system into a tem blocks. These are usually connected
finite number of homogeneous, well-mixed in cascade with the original process on ei-
subsystems called compartments or pools, ther its input or its output variables, or both.
which exchange materials with each other See also compensator, pre-compensator and
and with the environment. Usually the com- post-compensator.

c
2000 by CRC Press LLC