Page 78 - The Illustrated Dictionary of Electronics

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bar meter • baseband frequency response 63

disadvantage is that it does not provide a precise barrier potential The apparent internal dc poten-
indication. tial across the barrier (see BARRIER, 1) in a pn
barn Symbol, b. A non-SI unit of nuclear cross sec- junction.
tion equal to 100 square femtometers or 10 – 24 barrier strip A terminal strip having a barrier (see
square centimeters. This unit is approved as BARRIER, 2) between each pair of terminals.
compatible with SI (International System of
Units).
Barnett effect The development of a small amount
of magnetization in a long iron cylinder that is ro-
tated rapidly about its longitudinal axis.
barograph A recording barometer, using either a
drum recorder (pen recorder) or a computer to
store the data as a function of atmospheric pres-
sure versus time.
barometer An instrument for measuring atmo-
spheric pressure.
barometer effect A relation that appears to exist
between the intensity of cosmic rays and the at- barrier strip
mospheric pressure. It is an inverse relation; that
is, increasing pressure seems to correlate with re-
duced intensity of cosmic rays. It is said to be ap- barrier voltage The voltage required for the initia-
proximately to 1 or 2% per centimeter of mercury. tion of current flow through a pn junction.
barometric pressure The atmospheric pressure, Bartlett force See EXCHANGE FORCE.
usually given in inches of mercury. The average baryon A subatomic particle made up of three
barometric pressure at the surface of the earth is quarks.
just under 30 inches of mercury. base 1. In a bipolar transistor, the intermediate re-
bar pattern A series of spaced lines or bars (hori- gion between the emitter and collector, which
zontal, vertical, or both) produced on a television usually serves as the input or controlling element
picture screen by means of a BAR GENERATOR. of transistor operation. 2. A substance that dis-
It is useful in adjusting horizontal and vertical sociates in water solution and forms hydroxyl
linearity of the picture. (OH) ions. For example, sodium hydroxide. 3. The
barrage array An antenna array in which a string constant figure upon which logarithms are com-
of collinear elements are vertically stacked. The puted (10 for common logs, 2.71828 for natural
end quarter wavelength of each string is bent in logs). 4. The radix of a number system (e.g., base
to meet the end quarter wavelength of the oppo- 10 for the decimal system, base 8 for the octal
site radiator to improve balance. system, base 16 for the hexadecimal system, and
barrage jamming The jamming of many frequen- base 2 for the binary system). 5. A fixed non-
cies, or an entire band, at the same time. portable radio communications installation.
barrell distortion Television picture distortion base address The number in a computer address
consisting of horizontal and vertical bulging. that serves as the reference for subsequent ad-
barrier 1. The carrier-free space-charge region in a dress numbers.
semiconductor pn junction. 2. An insulating par- baseband The frequency band of the modulating
tition placed between two conductors or termi- signal in a communications, broadcast, or data
nals to lengthen the dielectric path. transmitter. For voice communications, this is
barrier balance The state of near equilibrium in a generally the range of voice frequencies necessary
semiconductor pn junction (after initial junction for intelligible transmission. For high-fidelity mu-
forming), entailing a balance of majority and mi- sic broadcasting, it is approximately the range of
nority charge carrier currents. human hearing. For fast-scan television, it
barrier capacitance 1. The capacitance in a bipolar ranges up to several megahertz. It can be re-
transistor between the emitter and collector. It stricted or expanded, depending on the nature of
varies with changes in applied voltage, and also the transmitted signal. See BASEBAND FRE-
with the junction temperature. 2. The capacitance QUENCY RESPONSE.
across any pn junction that is reverse-biased. baseband frequency response 1. The amplitude-
barrier height The difference in voltage between versus-frequency characteristic of the audio-
opposite sides of a barrier in a semiconductor frequency (AF) or composite video section of a
material. transmitter that defines the BASEBAND, or range
barrier layer See BARRIER, 1. of modulating frequencies. 2. The range of fre-
barrier-layer cell A photovoltaic cell, such as the quencies over which a radio transmitter can be
copper oxide or selenium type, in which photons modulated to convey information. For single side-
striking the barrier layer produce the potential band (SSB), it is approximately 300 Hz to 3 kHz;
difference. for high-fidelity, frequency-modulated (FM) music