Page 77 - The Illustrated Dictionary of Electronics

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62 bandstop filter • bar meter

bandstop filter See BAND-REJECTION FILTER. CODE. The laser beam moves across the tag. The
band suppression 1. The property of blocking, or beam is reflected from the white regions between
greatly attenuating, signals within a specific fre- the lines, but is absorbed by the dark lines them-
quency band. 2. The frequency limits between selves. This produces modulation of the reflected
which a device or circuit rejects or blocks ac en- beam by the data contained in the tag.
ergy, while passing energy at other frequencies bare conductor A conductor with no insulating cov-
with negligible loss. ering, a common example being bare copper wire.
band-suppression filter See BAND-REJECTION bar generator A special type of radio-frequency
FILTER. signal generator that produces horizontal or ver-
bandswitch A low-reactance selector switch (usually tical bars on the screen of a television receiver. It
rotary) that facilitates changing the tuning range of is used in adjustment of horizontal and vertical
a radio receiver, transmitter or transceiver from linearity.
one band of frequencies to another. bar graph A graphical presentation of data, in
bandswitching In a receiver, transmitter, or test which numerical values are represented by hori-
instrument, the process of switching self- zontal bars of width that correspond to the val-
contained tuned circuits to change from one fre- ues. This type of graph is nonstandard in the
quency spectrum to another within the range of sense that the ordinate is horizontal, whereas it is
the device’s intended operation. usually vertical. Compare COLUMNAR GRAPH.
bandwidth 1. For a communications or data sig- bar-graph meter See BAR METER.
nal, a measure of the amount of spectrum space barium Symbol, Ba. An elemental metal of the al-
the signal occupies. Usually, it is given as the dif- kaline-earth group. Atomic number, 56. Atomic
ference between the frequencies at which the sig- weight, 137.36. It is present in some compounds
nal amplitude is nominally 3 dB down with used as dielectrics (e.g., barium titanate).
respect to the amplitude at the center frequency. barium-strontium oxides The combined oxides of
These frequencies represent the half-power barium and strontium used as coatings of
points of the amplitude-versus-frequency func- vacuum-tube cathodes to increase electron emis-
tion. In general, the bandwidth increases as the sion at relatively low temperatures.
data rate (in bits per second, baud, or words per barium strontium titanate A compound of bar-
minute) increases. 2. Also called NECESSARY ium, strontium, oxygen, and titanium that is
BANDWIDTH. The minimum amount of spectrum used as a ceramic dielectric material. It exhibits
space normally required for effective transmis- ferroelectric properties and is characterized by a
sion and reception of a communications or data high dielectric constant.
signal. 3. See BANDPASS, 1. barium titanate Formula, BaTi0 2. A ceramic used
bank A collection of usually similar components as the dielectric in ceramic capacitors. It exhibits
used in conjunction with each other, usually in a high dielectric constant and some degree of ferro-
parallel configuration. Some examples are resis- electricity.
tor bank, lamp bank, and transformer bank. Barkhausen effect The occurrence of minute
banked transformers Parallel-operated trans- jumps in the magnetization of a ferromagnetic
formers. substance as the magnetic force is increased or
bankwound coil A coil wound in such a way that decreased over a continuous range.
most of its turns are not side by side, thus reduc- Barkhausen interference Interference that results
ing the inherent distributed capacitance. from oscillation because of the BARK-HAUSEN
bar 1. Abbreviation, b. The cgs unit of pressure, in EFFECT.
5
which 1 b = 10 pascals per square centimeter. 2. bar magnet A relatively long permanent magnet in
A horizontal or vertical line produced on a televi- the shape of a bar with a rectangular or square
sion (TV) screen by a bar generator and used to cross section.
check linearity. 3. A thick plate of piezoelectric bar meter A digital meter that displays a quan-
crystal. 4. A solid metal conductor, usually unin- tity, such as signal strength, incrementally, us-
sulated, of any cross section. 5. A silicon ingot ing a set of LEDs or LCDs arranged in a straight
from which semiconductor devices can be fabri- line. Its main advantage is that it has no moving
cated. parts, yet (unlike direct-readout digital meters)
BAR Abbreviation of BUFFER ADDRESS REGIS- gives the viewer some impression of the way a
TER. rapidly fluctuating quantity changes. Its chief
bar code A printed pattern that contains data that
can be recovered by laser scanning. It is com-
monly used for the pricing and identification of
store merchandise. It can also be used by an as-
sembly or maintenance robot as an aid to identi-
fying tools.
bar-code reader A laser scanning device that re-
covers the data from a tag that contains a BAR