azimuth.
The angle that measures
deviation with respect to the south in
the northern hemisphere, and with
respect to the north in the southern
hemisphere. See also:
inclination
B
bandwidth.
A measure of fre-
quency ranges, typically used for
digital communications.
The word
bandwidth is also commonly used
interchangeably with
capacity
to
refer to the theoretical maximum
data rate of a digital communica-
tions line. See also:
capacity,
channel, throughput
battery.
A device used to store en-
ergy in a photovoltaic system. See
also:
solar panel, regulator, load,
converter, inverter
beamwidth.
The angular distance
between the points on either side of
the main lobe of an antenna, where
the received power is half that of the
main lobe. The beamwidth of an
antenna is usually stated for both
the horizontal and vertical planes.
benchmarking.
Testing the maxi-
mum performance of a service or
device.
Benchmarking a network
connection typically involves
fl
ood-
ing the link with traf
fi
c and measur-
ing the actual observed throughput,
both on transmit and receive.
BGAN
see
Broadband Global Ac-
cess Network
BNC connector.
A coaxial cable
connector that uses a "quick-
connect" style bayonet lug. BNC
connectors are typically found on
10base2 coaxial Ethernet.
bridge.
A network device that con-
nects two networks together at the
data link layer
.
Bridges do not
route packets at the
network layer
.
They simply repeat packets between
two
link-local
networks.
See also:
router
and
transparent bridging
fi
rewall
.
bridge-utils.
A Linux software
package that is required for creat-
ing 802.1d Ethernet bridges.
Broadband Global Access Net-
work (BGAN)
.
One of several stan-
dards used for satellite Internet ac-
cess.
See also:
Digital Video
Broadcast (DVB-S)
and
Very Small
Aperture Terminal (VSAT)
.
broadcast address.
On IP net-
works, the broadcast IP address is
used to send data to all hosts in the
local subnet.
On Ethernet networks,
the broadcast MAC address is used
to send data to all machines in the
same collision domain.
bypass diodes.
A feature found on
some solar panels that prevents the
formation of
hot-spots
on shaded
cells, but reduces the maximum
voltage of the panel.
C
CA
see
Certi
fi
cate Authority
Cacti
(
).
A
popular web-based monitoring tool
written in PHP.
Glossary
391

capacity.
The theoretical maximum
amount of traf
fi
c provided by a digi-
tal communications line.
Often used
interchangeably with
bandwidth
.
captive portal.
A mechanism used
to transparently redirect web brows-
ers to a new location.
Captive por-
tals are often used for authentication
or for interrupting a user's online
session (for example, to display an
Acceptable Use Policy).
cell.
Solar panels are made up of
several individual cells, which are
electrically connected to provide a
particular value of current and volt-
age. Batteries are also made up of
individual cells connected in series,
each of which contributes about 2
volts to the battery.


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