Page 233 - Electrical Engineering Dictionary

multipath energy arriving at amobilereceiver from the balance condition and the unknown
from differing directions. resistor can be found using the same formula
as in an ordinary Wheatstone bridge.
Doppler-free spectroscopy a spectro-
scopic technique in which two or more light double buffering (1) generally, any
fields are used to produce a spectral line that buffering scheme where two identical mem-
is not Doppler shifted or Doppler broadened. ory images are used. One memory image
For example, in the case of lambda systems is used to hold received data, while data is
or vee systems, this requires that the elec- simultaneously read from the other memory
tromagnetic fields co-propagate, whereas for image.
cascade systems, the fields must counter-
(2) in terminal-to-computer communica-
propagate.
tion scheme where a number of remote ter-
minals are connected to a single computer
DOS See disk operating system.
through a “multiplexer.” This unit connects
n low-speed bit-serial transmission lines onto
dose to clear the amount of exposure
a single high-speed bit-serial line (running n
energy required to just clear the resist in a
times faster) using STDM (synchronous time
large clear area for a given process.
division multiplex) of the connection. In the
multiplexer, each low-speed line isconnected
dosimeter an instrument used for mea-
to a “one-character buffer,” converting the re-
suring or evaluating the absorbed dose of ra-
ceived low-speed bitstream to a high-speed
diation. It may depend on the measurement
bitstream using two shift-registers (buffers).
of ionization for its operation or may simply
The first one receives the low-speed line char-
involve the darkening of a piece of photo-
acter bits (8 bits), clocked by the low-speed
graphic film ("film badge").
“receive clock.” When a complete charac-
ter has been received, it is moved to the
dot pitch the center-to-center distance be-
second shift-register, where it is stored un-
tween adjacent green phosphor dots of the
til it can be shifted out on the high-speed
red, green, blue triad in a color display.
line on the appropriate time slot. Mean-
while, the next character is assembled in the
dot-matrix printer a printer that pro-
first shift-register. For full-duplex operation
duces readable characters by imprinting a
(simultaneous two-way communication), a
large number of very small dots.
similar structure is needed for the opposite
(computer-to-terminal) connection.
dots per inch (DPI) a measure of the den-
sity of line-printer plots in dots per inch.
double conversion the process where an
double bridge a Wheatstone bridge mod- incoming RF signal is mixed with a local os-
ification designed to increase the precision cillator (LO) signal to produce the first inter-
of measurements for low-value resistors. To mediate frequency (IF). This IF is then mixed
avoid the error due to resistance of the con- with a second fixed LO to produce a second
nection (called yoke) between the unknown IF signal.
resistor and the standard resistor, the ends of
the unknown resistor and the standard resis- double conversion receiver a receiver
torareconnectedtothebalancedetector(usu- that uses two heterodyne operations be-
ally a galvanometer for this type of bridge) fore detection generating two intermedi-
via two small resistors, the ratio of which is ate frequencies, first intermediate frequency
the same as the ratio of resistors in the ratio (IF) and second IF, respectively. See also
arms. Then the yoke resistance is eliminated intermediate frequency.

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