Page 205 - Electrical Engineering Dictionary

delta modulation in signal processing. The demand assign multiple access protocol
difference between the control reference and telephone signalling mechanism in which the
the switched signal is integrated and fed to access is established for the duration of a call.
a Schmitt trigger. When the integrated value
reaches a predefined upper bound the switch demand fetch in a cache memory, the
is turned off. When the integrated value name given to fetching a line from the mem-
reaches a predefined lower bound the switch ory into the cache on a cache miss when it is
is turned on. requested and not before.

demand meter an electric meter which
delta rule a supervised learning algo-
shows both the energy used and the peak
rithm, based upon gradient descent, that was
power demand in a given period.
developed for application to single-layer net-
works of linear threshold units. For each
input pattern x, the weight wij connecting demand paging condition where each
input xj to unit i is adjusted according to page in virtual memory is loaded into main
Dwij = h(ti − wi · x)xj, where wi is the memory, after first being referenced by the
vector of weights wij, ti is the target output processor (i.e., not in advanced). The first
for unit i, and h is a positive constant. This reference to each page will thus always cause
rule is also known as the Widrow–Hoff rule a “page fault” (page not in main memory).
and the LMS algorithm. After these initial page faults, most of the
pages needed by the program are in main
memory.
delta–delta transformer a three-phase
transformer connection formed by connect-
demodulation the process by which a
ing three single-phase transformers in which
modulated signal is recovered back to its
the windings on both the primary and the sec-
original form. It is the general process
ondary sides are connected in series to form
of extracting the information-bearing signal
a closed path.
from another signal. Modulation is the gen-
eral process of embedding an information-
delta-wye transform a transformation bearing signal into a second carrier sig-
between delta and wye connections. nal. An important objective in modulation is
to produce a signal whose frequency range
is suitable for transmission over the com-
delta–wye transformer a three-phase
munication channel to be used. See also
transformer connection formed by connect-
modulation.
ing three single-phase transformers in which
the primary windings are connected in series
to form a closed path while one end of each DeMorgan’s theorem a formula for find-
of the secondary windings is connected to a ing the complement of a Boolean expression.
common point (the neutral). It has two forms:
1. A ∨ B = A ∧ B
demagnetization the act of removing a 2. A ∧ B = A ∨ B
device from being in a magnetic state, i.e.,
where A and B are Boolean variables and ∧
rearranging the atomic magnetic domains in
represents logical AND and ∨ represents log-
a disoriented fashion.
ical OR and the overbar represents the logical
complement.
demagnetizing field the magnetic field
produced by divergences in the magnetiza- demultiplexer a logic circuit with K in-
tion of a magnetic sample. puts and I controls which steers the K inputs

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2000 by CRC Press LLC