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AXIS M32 Series - Glossary of Terms
translate Internet domain names into IP (Internet Protocol)
addresses. A domain name is a meaningful and
easy-to-remember name for an Internet address. For
example the domain name www.example.com is much
easier to remember than 192.0.34.166. The translation
tables for domain names are contained in Domain name
servers.
Domain Server -
Domains can also be used by
organizations who wish to centralize the management of
their (Windows) computers. Each user within a domain has
an account that usually allows them to log in to and use
any computer in the domain, although restrictions may
also apply. The domain server is the server that
authenticates the users on the network.
Duplex -
See
Full-duplex.
Ethernet -
Ethernet is the most widely installed local area
network technology. An Ethernet LAN typically uses
special grades of twisted pair wires. The most commonly
installed Ethernet systems are 10BASE-T and
100BASE-T10, which provide transmission speeds up to 10
Mbps and 100 Mbps respectively.
ETRAX (Ethernet Token Ring AXIS) -
Axis' own
microprocessor.
Factory default settings -
These are the settings that
originally applied for a device when it was first delivered
from the factory. If it should become necessary to reset a
device to its factory default settings, this will, for many
devices, completely reset any settings that were changed
by the user.
Firewall -
A firewall works as a barrier between networks,
e.g. between a Local Area Network and the Internet. The
firewall ensures that only authorized users are allowed to
access the one network from the other. A firewall can be
software running on a computer, or it can be a standalone
hardware device.
Focal length -
Measured in millimeters, the focal length of
a camera lens determines the width of the horizontal field
of view, which in turn is measured in degrees.
FTP (File Transfer Protocol) -
An application protocol that
uses the TCP/IP protocols. It is used to exchange files
between computers/devices on networks.
Frame -
A frame is a complete video image. In the 2:1
interlaced scanning format of the RS-170 and CCIR
formats, a frame is made up of two separate fields of 262.5
or 312.5 lines interlaced at 60 or 50 Hz to form a complete
frame, which appears at 30 or 25 Hz. In video cameras with
a progressive scan, each frame is scanned line-by-line and
not interlaced; most are also displayed at 30 and 25 Hz.
Frame rate -
The frame rate used to describe the frequency
at which a video stream is updated is measured in frames
per second (fps). A higher frame rate is advantageous when
there is movement in the video stream, as it maintains
image quality throughout.
Full-duplex -
Transmission of data in two directions
simultaneously. In an audio system this would describe e.g.
a telephone systems. Half-duplex also provides
bi-directional communication, but only in one direction at
a time, as in a walkie-talkie system. See also
Simplex
.
Gain -
Gain is the amplification factor and the extent to
which an analog amplifier boosts the strength of a signal.
Amplification factors are usually expressed in terms of
power. The decibel (dB) is the most common way of
quantifying the gain of an amplifier.
Gateway -
A gateway is a point in a network that acts as
an entry point to another network. In a corporate network
for example, a computer server acting as a gateway often
also acts as a proxy server and a firewall server. A gateway
is often associated with both a router, which knows where
to direct a given packet of data that arrives at the gateway,
and a switch, which furnishes the actual path in and out of
the gateway for a given packet.
GIF (Graphics Interchange Format) -
GIF is one of the most
common file formats used for images in web pages. There
are two versions of the format, 87a and 89a. Version 89a
supports animations, i.e. a short sequence of images within
a single GIF file. A GIF89a can also be specified for
interlaced presentation.
GOV (Group Of VOPs) -
A group of VOPs is the basic unit
of an H.264 video stream. The GOV contains different
types and numbers of VOPs (I-VOPs, P-VOPs) as
determined by the GOV length and GOV structure. See also
VOP
.
GOV length -
The GOV length determines the number of
images (VOPs) in the GOV structure. See also
GOV
and
VOP
.
GOV structure -
The GOV structure describes the
composition of an H.264 video stream, as regards the type
of images (I-VOPs or P-VOPs) included in the stream, and
their internal order. See also
GOV
and
VOP
.
H.264 -
A standard for video compression, also known as
MPEG-4 Part 10.
Half-duplex -
See
Full-duplex
.
HTML (Hypertext Markup Language) -
HTML is the set of
"markup" symbols or codes inserted in a file intended for
display in web browser. The markup tells the browser how
to display the page's words and images for the user.
HTTP (Hypertext Transfer Protocol) -
HTTP is the set of
rules for exchanging files (text, graphic images, sound,
video, and other multimedia files) on the web. The HTTP
protocol runs on top of the TCP/IP suite of protocols.
Hub -
A (network) hub is used to connect multiple devices
to the network. The hub transmits all data to all devices
connected to it, whereas a switch will only transmit the
data to the device it is specifically intended for.
IEEE 802.11 -
A family of standards for wireless LANs. The
802.11 standard supports 1 or 2 Mbit/s transmission on the
2.4 GHz band. IEEE 802.11b specifies an 11 Mbit/s data
rate on the 2.4 GHz band, while 802.11a allows up to 54
Mbit/s on the 5 GHz band.
