Page 93 - Electrical Engineering Dictionary

or word is processed in W clock cycles. In black burst a TV black video signal
contrast, all W bits of a word are processed in containing horizontal and vertical sync, color
the same clock cycle in a bit-parallel system. burst, and setup (i.e., a composite video black
For example: a bit serial adder with 4- signal). Black burst is also called “color
bit data has one input signal for each of data black.” A black burst signal is often used
them, one bit for carry-in, and two 4-bit shift in the video studio to provide synchronizing
registers for data. pulses.

bit-line capacitance the equivalent ca- black level the portion of the video sig-
pacitance experienced in each “bit line” in a nal pertaining to the lower luminance (bright-
RAM or ROM device. See also bit line. ness) levels.

bit-oriented block transfer (bitBLT) a black start the task of re-starting an iso-
type of processing used mainly for video in- lated power system which is completely de-
formation characterized by minimal opera- energized. Most generating plants require
tions performed on large data blocks; a pro- substantial external electric power to start.
cessor designed for such operations. bit- Thus a black start may be initiated by hand-
BLT operations include transfers, masking, starting gas turbine generators or by opening
exclusive-OR, and similar logical functions. the gates of a hydroelectric generator some-
where in the system.
bit-serial system a system that uses bit
serial data transfer.
blackbody theoretically contrived object
that gives rise to the so-called “black body ra-
bit-slice processor a processor organiza-
diation.” One might imagine a closed surface
tion that performs separate computations (via
object (say of metal) possessing one open-
multiple processing units) separately upon
ing that connects the interior surface with the
subsections of an incoming channel.
outside world. When the object is heated, the
opening becomes a perfect “black” radiator.
bitBLT See bit-oriented block transfer.
Such radiation depends on temperature only.
bitmapped image a digital image com-
blackout total loss of power to the entire
posed of pixels. Bitmapped images are
power system.
resolution-dependent, i.e., if the image is
stretched, the resolution changes. Also
blanket an insulating rubber mat which is
called a raster image. See also image, pixel,
fitted temporarily over energized conductors
vector image.
to protect nearby workers.
bits per pixel the number of bits used to
represent each pixel in a digital image. Typ- blanking the electronic control circuitry
ical grayscale images have 8 bits per pixel, that blanks the television raster during hori-
giving 256 different gray levels. True color zontal and vertical retrace.
images have 24 bits per pixel, or 8 bits for
each of the red, green, and blue pixels. Com- blanking time the short time interval
pressed image sizes are often represented in when both switches in a leg of an inverter
bits per pixel, i.e., the total number of bits bridge must be off in order to prevent short
used to represent the compressed image di- circuiting the DC input. This is necessary be-
vided by the total number of pixels. cause non-ideal switches cannot turn on and
off instantaneously. Thus, after one switch is
BJT See bipolar junction transistor. turned off in an inverter leg, the complimen-

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2000 by CRC Press LLC