Specifications

122 VISTA AT A GLANCE V5 - FOR MORE INFORMATION VISIT: V I S T A - C C T V. C O M / I P
GLOSSARY OF TERMS
Depth of Field - The area of acceptable focus of an image. The wider
you set the aperture of a lens the lower the depth of field becomes.
DHCP (Dynamic Host Configuration Protocol) - DHCP is a protocol
that lets network administrators automate and centrally manage the
assignment of Internet Protocol (IP) addresses to network devices in a
network.
Dialup Line - A two way line used in Public Switched Telephone Network
(PSTN)
Digital - A signal that levels are represented by binary numbers. These
can be kept in a store.
Digital Signal Processing (DSP) - An algorithm within the camera that
digitises data (the image). Examples include automatic compensate
for backlight interference, colour balance variations and corrections
related to aging of electrical components or lighting. Functions such as
electronic pan and zoom, image annotation, compression of the video
for network transmission, feature extraction and motion compensation
can be easily and inexpensively added to the camera feature set.
DIN Connector (Deutsches Institute fur Normung) - A German
Standards Institute connector. A family of plugs and sockets used to
connect mice, keyboards and various audio devices.
Distortion - The deviation of the received signal waveform from that of
the original transmitted waveform.
Distribution Amplifier - A device that accepts a video signal and sends
it out over a number of independent outputs.
DNS (Domain Name System) - DNS is used to locate and translate
Internet domain names into IP (Internet Protocol) addresses.
DRC (Dynamic Range Control) - Visibly brightens the subject in a dark
area
Dry Contact - A contact that is isolated or unconnected from any
electrical source.
DSL (Digital Subscriber Line) - A family of technologies that provide
digital data transmission over the wires of a local telephone network.
Examples include ADSL (Asymmetric DSL) where upload speeds are less
than download and SDSL (Symmetric SDSL) where data speeds are the
same in both directions.
DVD (Digital Video Disk, Digital Versatile Disk) - A de facto standard
agreed on by the computer, consumer electronics and entertainment
industries for storing 4.7GB or more data on a single optical disk the size
of a CD.
DVR (Digital Video Recorder) - See Hard Disk Recorder.
D-WDR - Digital Wide Dynamic Range allows the installer to resolve
highly contrasting scenes of view to provide a more balanced image.
Dwell Time - The length of time a switcher will hold a camera before
moving on to the next in sequence.
EHLC (Excessive Highlight Compensation) - The brighest part of the
picture is dimmed to allow the other areas to be viewed.
EI (Electronic Iris) - Automatically varies a CCD camera’s shutter to
mimic Auto Iris control, allowing fixed or manual iris lenses to be used in
a wider range of areas.
EIA (Electronic Industries Association) - A standards organisation in
the US specialising in the electrical and functional characteristics of
interface equipment.
Encoded - The result of transferring information in a coded form to a
medium.
EOL - End Of Line.
EPROM (Erasable and Programmable Read Only Memory) - An
electronic chip used in many different security products that stores
software instructions for performing various operations.
Ethernet - Ethernet is the most widely installed local area network
technology. The most commonly installed Ethernet systems are
10BASE-T and 100BASE-T10, which provide transmission speeds up to 10
Mbps and 100 Mbps respectively. A local area network (LAN) developed
by Xerox, Digital Equipment Corp. and Intel. Standardised as IEEE 802.3
and ISO 8802.3. Ethernet connects up to 1024 nodes at 10 Mbps over
twisted-pair, coax and fibre optic cable. When a station is ready to send,
it transmits its data packets onto the network, which is common to
all nodes. All stations “hear” the data. The station that matches the
destination address in the packet responds while the others do nothing.
Ethernet is a data-link protocol and functions at the Physical and Data-
link Levels of the OSI model (Layers 1 and 2).
Ethernet Address - A unique 48-bit number maintained by the IEEE/
ISO and assigned to each Ethernet network adapter.
Ext. Sync (External Sync) - The ability of CCTV equipment, normally
cameras, to accept one or more of the standard sync formats so as to
align itself to the rest of the system.
External Sounder - A device which gives an audible and visual
verification of an alarm activation.
EXview™ - The latest interline CCD sensor from Sony that has increased
sensitivity across the visible spectrum and the near IR.
Fibre Optic - The process of transmitting light through a long, flexible
fibre such as glass or plastic, for the purpose of transmitting video,
audio, or data over long distances.
Field - One half of a frame, consisting of either the odd or the even
numbered lines. 50 fields are transmitted every second.
Field of View - The view achieved with a particular lens; varies with the
focal length.
File - The orderly arrangement of data or information.
Firewall - A firewall works as a barrier between networks, e.g. between
a Local Area Network and the Internet. The firewall ensures that only
authorised users are allowed to access the one network from the other.
Flash memory - A memory chip that holds its content without power
but must be erased in fixed blocks rather than single bytes. Block sizes
typically range from 512 bytes up to 256KB.
FLK/FLC - Setting in cameras that will allow the camera to work with
50hz fluorescent lights to keep the camera from pulsing.
Focal Length - Of a lens, the distance in millimetres, between its
secondary principal point and its focal point. The higher the number the
greater the magnification and the less the field of view.
Focal Point - The point on the axis of a lens to which parallel rays of
light will cover.
Focus Range - The range of distances a projection unit can be from
a target surface/screen. It is recommended the projection unit be
mounted or placed within this distance to ensure optimum image quality
and clarity.