Page 194 - Electrical Engineering Dictionary

tency is not necessarily improved. See also quence by a program counter as in a tradi-
disk array. tional von Neumann computer. More than
one processor is present to execute the in-
data structure a particular way of orga- structions simultaneously when possible.
nizing a group of data, usually optimized for
efficient storage, fast search, fast retrieval, Daubechies wavelets a class of com-
and/or fast modification. pactly supported orthogonal and biorthog-
onal wavelets, first proposed by Ingrid
data tablet a device consisting of a sur- Daubechies, that can be obtained by impos-
face, usually flat, and incorporating means ing sufficient conditions on wavelet filters.
for selecting a specific location on the sur-
face of the device and transmitting the coor- daughter board a computer board that
dinates of this location to a computer or other provides auxiliary functions, but is not the
data processing unit that can use this infor- main board (motherboard) of a computer sys-
mation for moving a cursor on the screen of tem (and is usually attached to the mother-
the display unit. board).

data terminal equipment (DTE) a de- dB See decibel.
vice, such as a subscriber’s computer, Ex-
dBc ratio of the signal power (p) to a ref-
change workstation, or Exchange central sys-
erence signal power (p ref ), usually the mod-
tem, that controls data flow to and from a
ulation carrier signal, expressed in decibels
computing system. It serves as a data source,
referenced to a carrier (dBc). Thus a har-
data sink, or both, and provides for the data
monic signal that is 1/100th of the power in
communicationcontrolfunctionaccordingto
a desired fundamental signal is at −20 dBc.
protocols. Each DTE has an address that is
a 12-digit number uniquely identifying the p
subscriber’s connection to the network. DTE P dBd = 10 log 10
p ref
term is usually used when referring to the RS-
232C serial communications standard, which
defines the two end devices of the communi- dBm Power ratio in decibels referenced
cations channel: the DTE and the DCE (data to 1 milliwatt.
communications equipment). The DCE is
usually a modem and the DTE is a UART DBS See direct broadcast satellite.
chip of the computer.
DBS receiver electronic assembly that
data-oriented methodology an applica- accepts as input a microwave signal from a
tion development methodology that consid- satellite, containing transmitted TV signals
ers data the focus of activities because data “modulated” onto the signal. The receiver
are more stable than processes. first amplifies the low-level signal, then pro-
cesses the signal by first converting it to a
database computer a special hardware lower “IF” frequency and then demodulating
and software configuration aimed primarily the signal to separate the TV signals from
at handling large databases and answering the microwave carrier signal. A basic way of
complex queries. looking at the relationship of the microwave
carrier to the TV signal is to think of the car-
dataflow computer a form of computer rier signal as an envelope with a message
in which instructions are executed when the letter inside. The message letter is the TV
operands that the instructions require become signal. Demodulation is the process of care-
available rather than being selected in se- fully removing the message from the enve-

c
2000 by CRC Press LLC