Glossary of Video Terms
Glossary of Video Terms
AGC (Automatic Gain Control)
AGC increases the signal strength of security cameras when the light level
decreases, and puts a cap on it during higher levels; this keeps the output
signal consistent.
AI (Auto Iris)
A useful feature to have in a video camera, an auto iris compensates for
variations in light levels, from sunlight to shadows. Essentially, the auto iris
opens and closes the lens iris as the light changes; this also prevents the
camera from being damaged by very bright sunlight.
Alarm Input
When attached to a security camera, an alarm input provides enhanced
security in the form of a sensor device, often a door contact or a Passive
Infra-red detector for motion detection. Alarm inputs can be self powered or
can require external power (usually 12V).
ALC (Automatic Level Control)
Some security cameras feature ALC, which means the camera can bring out
detail in bright or dark areas of an image. If too much sunlight makes an
image too dark, ALC can focus on the needed image.
Its general definition means a set of mathematical instructions to solve a
task. In the field of video technology, they enable digital compression of the
video picture.
Ambient Light Level
This is the amount of background light present at any specific time.
Analog Signal
Analog signals are produced by most security cameras. Analog signals are
continuously variable, and are greatly affected by ‘noise’ (disturbances)
within the system, and recordings of analog information (such as videotapes)
degrade over time. This doesn’t occur with digital signals recorded on media
like CDs, DVDs and computer hard drives.
Angle of view
Also known as viewing angle, this refers to the angular range available within
a certain image size. The smaller the focal length, the wider the angle of
view is.
This is a signaling device, either visual or audio based. For example, wireless
annunciators use infrared beams that trigger an audible signal when
interrupted, and can be used for security or retail purposes.
An aperture is a lens opening that controls how much light reaches the film
or digital sensor. Iris adjustment controls aperture size, and a series of fstop numbers dictate how much light passes through the lens. A smaller
aperture allows for better focus on objects outside the camera’s plane of
Aspect Ratio
Aspect Ratio refers to the ratio between an image’s height and width.
Differing mediums such as television, HDTV, and film, use different aspect
ratios. Within computer graphics, it refers to the shape of an individual pixel
in a digital image.
A reduction in light strength or electrical signal, usually because of absorption
or scattering, is called attenuation. The use of triaxial cables can minimize
AVC (Advanced Video Coding)
Both the ITU and MPEG groups have agreed upon AVC as the current video
compression standard. ITU calls it H.264, the MPEG group refers to it as
MPEG-4, and the public calls it AVC.
Biometrics is the technology and science of authenticating individuals by
measuring their physiological or behavioral features. In the field of security,
they are technologies (‘readers’) used to analyze fingerprints, voice patterns,
irises or retinas, etc.
This refers to the defocusing and glow present around the bright areas of a
picture when the brightness is increased. Some video cameras feature
blooming suppression abilities to avoid this.
BNC connector
These are a type of RF connectors that interconnect two coaxial cables or
connect a cable with CCTV components. They’re used in Ethernet networks,
video connections, network cards, and cable interconnections.
bps (Bits Per Second)
This unit is used to measure the speed data is moved between sources. For
example, a 56kbps modem can move 56,000 bits per second.
Bullet Camera
Named in reference to its shape, a bullet camera is a type of security camera
similar to a spot cam. Its limitation is a fixed focal lens (not zoom), but its
small, narrow size makes it suitable for areas other cameras might not fit.
A unit of eight bits is known as a Byte.
A candela is a measurement of luminous intensity and is a replacement to
the candle.
CCTV (Closed Circuit Television)
CCTV refers to the use of television cameras for surveillance purposes.
Unlike broadcast television, all devices are linked directly, usually by cables.
CCTV pictures are viewed and/or recorded, but are not broadcast. Usually
involving analog cameras and recorders, CCTV is the precursor to digital
network systems.
The use of Complementary Metal-Oxide Semiconductors in imagers to sense
images improves over CCD technology in resolution, dynamic range, and
noise sensitivity.
This is a specific type of camera, as well as its corresponding lens mount.
The C-mount lens is found in older versions of security cameras, and has a
flange back distance of 17.5mm. In order to achieve a focused image, a
5mm ring must be inserted between the camera and lens.
Coaxial Cable
A cable with a central conductor that’s surrounded by a shield sharing its
same axis is called a coaxial cable. It’s used primarily for carrying high
frequency or broadband signals. RG59 video coaxial cable is used for digital
video recorder (DVR) installations.
Composite Video
This type of video is a combination of different source video signals, usually
YUV, field, line, blanking pedestal, color sync, and field equalizing pulses.
The end result is one composite signal, allowing it to be modulated onto a RF
A concave optical lens has an inward curving surface, causing incoming light
to diverge.
A convex lens curves outwards, and is sometimes known as converging.
Light that passes through converges to a focal point.
A CCTV surveillance system that uses hidden cameras and lenses is
considered to be covert.
CRT (Cathode Ray Tube)
The CRT is a tube found in most televisions, monitors, and video monitors.
Once heated, it creates images by emitting a beam of electrons that hit a
phosphor-coated surface. The glow of the surface is dependent on the
beam’s intensity. Each CRT uses deflection circuitry to control the beam’s
CS Mount
CS mount lenses offer a longer focal distance than their C mount
predecessors. They have a flange back distance of 12.5mm. Because they
are more practical for compact cameras, CS mounts are used in most
modern cameras. A 5mm spacer ring (known as a C ring) enables CS
cameras to also use a C mount lens.
dB (Decibel)
A decibel is a logarithmic unit that measures the loudness, power, or
strength of a signal.
DC (Direct Current)
DC differs from AC (alternating current) in that electricity always flows
thorough it in the same direction. A pair of wires has one positive wire and
one negative. Many security cameras are 12 Volt DC, although some can
operate at different voltages.
Default Gateway
In order to send data or video between networks, the IP Address of the
Router is required. This address is known as the Default Gateway.
This refers to the procedure of separating different channels of video, audio,
or data that were multiplexed at the source.
Depth of field
This is the difference between the nearest and furthest points in a scene that
remain in sharp focus. Depth of field is dependent on the F-stop and focal
length of the lens.
DHCP (Dynamic Host Configuration Protocol)
A DHCP refers to the protocol used by a host computer to obtain an IP
address so that it can communicate with other host computers. These
addresses are usually dynamic, meaning they change periodically, so a
connection cannot be obtained (or maintained) over the open Internet. Use
of both static IP addresses and dynamic DNS helps establish a consistent
Digital Signal
A sequence of binary bits that represent ones and zeros makes up a digital
Distribution Amplifier
This device amplifies and distributes an audio or video signal to multiple
outputs, such as several video monitors or recording devices. This device
allows the maintenance of the original signal’s output impedance to avoid
mismatches which could reduce the power required to properly drive the
signal’s end point.
DivX Networks created DivX, a MPEG-4 digital video technology. Among its
benefits is compression technology, which allows DivX equipped network
cameras to store a month of video on a 20’gigabyte hard drive.
DNS (Domain Name Service)
DNS is the system that matches server IP addresses to web site domain
Dome Camera
A common indoor security camera, dome cameras are mounted on the
ceiling. Their two main advantages are a more appealing visual appearance
and being easily movable. Their drawback is a lack of usefulness during low
light situations (therefore not effective when the lights are off).
DSL (Digital Subscriber Line)
DSL is a digital telecommunications protocol that allows existing copper
phone lines to be used for high-speed transfer of data between home and
business end-users. xDSL refers to the various types of Digital Subscriber
Lines which include: ADSL (Asymmetric DSL), SDSL (Single-line DSL), HDSL
(High-data-rate DSL) and VDSL (Very-high-data-rate DSL). In theory, ADSL
(the most common of these types), allows for download speeds of up to 9
Mbps and upload speeds of up to 640 Kbps. In reality, commercial
performance is normally up to 1.544 Mbps download and 128 Kbps upload.
DSP (Digital Signal Processing)
These chips can compress video independent of the CPU, which avoids the
need to draw processing power from the CPU, allowing it to focus on other
applications and computing tasks.
DTMF (Dual Tone Multi-Frequency)
The scientific term for the Touch Tone signal used on telephones, it is the
existing standard for the use of twisted wire pairs to send signals. Some PTZ
cameras use DTMF signals in the transferring of telemetry information to the
camera. This allows users to move the camera by dialing the number for
that camera and then pressing buttons on their phone.
A type of multiplexer that allows you to simultaneously record images to tape
and display live multiple-picture (or single picture) screen images of security
cameras. Another capability that is provided is the ability to record images
on one VCR while at the same time playing back previously recorded images
on a second VCR. Compare with a simplex multiplexer which provides less
features and capabilities.
DVR (Digital Video Recorder)
This device transforms analog video signals from security cameras into digital
format, suitable for storage on a hard drive. It also helps the user manage
the stored video files, as well as providing motion detection settings and PTZ
security camera control. DVRs can often be remotely accessed over the
Dwell Time
The time a multiplexer or DVR stays on an individual camera before moving
onto the next one in the sequence is known as dwell time.
Dynamic IP address
This is the rotation of IP addresses such that every time a user logs onto the
Internet, their IP address changes. This is done for Internet security
purposes, either by the user or by their ISP. This process can interfere with
the use of networked devices such as Network IP Cameras because they
normally require a static IP address to function properly.
Dynamic Range
A camera with a wide dynamic range is able to operate in variable light
conditions (known as lux levels), especially those of low light. A “dB” is
usually the unit used to measure the dynamic range of security cameras,
with more being better. A camera with a 60 dB dynamic range would be well
suited to clearly record a scene in low or high light levels.
EI (Electronic Iris)
Certain CCD security cameras utilize an electronic iris to electronically mimic
a traditional auto iris. One drawback of an EI is that excessive light damages
it over the long term.
EIA (Electronic Industries Association)
EIA is both an electronics trade organization that develops industry standards
and a term associated with serial communications applicable to digital video
Electronic Shuttering
This term applies to video cameras that compensate for moderate indoor
changes in light without use of auto iris lenses.
E-mail notification
This is a feature of certain motion detecting Network IP Cameras. When
activity is detected, they can email authorized users images or video. Griffid
is one example of camera management software that accomplishes this.
Embedded operating system
Cameras with this can also operate as computers. With an OS like Linux
installed, they can perform other tasks such as sending images to a web site
via FTP, email notification, and being simultaneously accessible by multiple
EMI (Electro Magnetic Interference)
If improperly shielded, most electronic equipment causes EMI. The FCC sets
the standards for electronic equipment shielding.
Ethernet can send information either wirelessly (known as WiFi) or, more
commonly, over wires. It runs at 10mbps, and all terminals connect to a
single common bus (sometimes called a highway). It serves as the IEEE
(Institute of Electrical and Electronics Engineers) 802.3 standard, which
ensures that networks adhere to a particular set of technical standards. A
new type, known as Fast Ethernet, or 100Base-T, runs at 100Mbps, and the
newest type, Gigabit Ethernet, runs at 1gigabit per second.
Event recorder
This type of recorder is kept in pause mode, and only records if activated by
an alarm.
Fence disturbance sensor
The perimeter fence around a site may have one of these installed around it
for intrusion detection. These sensors can be interfaced with a CCTV
switcher so that specific cameras are activated in an area where the
disturbance is detected.
FI (Fixed Iris)
These widely used fixed focal length iris lenses are inexpensive and are found
in smaller types of fixed CCTV security cameras, usually small case or dome
Fiber Optics
These high-speed computer-networking cables transmit data using light
instead of copper.
A field is one half of a frame, with 262.5 lines in the NTSC standard.
Interlaced television monitors display their images in two steps. The first
step paints every other line, while the second paints the remaining ones.
Progressive monitors present a complete field with each frame. Sixty fields
are transmitted each second.
Field of view
This is the total height and width of the view seen through the lens.
A firewall is a software or hardware application installed on a home or office
computer that is intended to prevent unauthorized users from accessing that
computer. With hacking and network intrusions on the rise, they are
becoming essential in protecting private information. Four popular types of
firewall are packet filtering, application gateways, circuit-level gateways, and
proxy servers. Although they can be difficult to configure correctly, they are
a critical component to protect unauthorized access and hacking of IP based
surveillance systems that are LAN based.
This is used to indicate image brightness as formed by the lens and
controlled by the iris. The smaller the f-number, the brighter the image is.
Focal Length
Focal length is measured in mm or inches, and is the distance between the
optical center of the lens and the point on which it focuses. A lower focal
length results in less magnification with a greater field of view, and vice
versa for longer focal lengths. Security cameras usually have a focal length
of _”, 1/3”, or _”.
fps (Frames Per Second)
In the field of video surveillance, fps means the number of frames a DVR is
able to capture per second. Three steps are required: video capture,
compression, and storage. Each step affects a DVR’s true fps number. The
use of DSP chips in both IP cameras and DVRs can assist in the optimization
of fps.
One complete picture is called a frame, and it contains 525 lines (NTSC) or
625 lines (PAL).
The light gathering ability of a lens (known as a camera lens aperture
setting) is indicated by an f-stop. Using a smaller f-stop number results in a
greater amount of light passing through the lens, as well as a shallower
depth of field.
FTP (File Transfer Protocol)
FTP is a client/server protocol used for the exchange of data between
computers. Network cameras with an embedded operating system use FTP
to send camera images to an authorized user’s computer or web site.
Gamma correction
This refers to an automated correction installed into surveillance cameras
that adjusts for the brightness characteristic of the monitor, with the range
being from .6 to 1.
Also known as ghosting, this is when an image moved across a computer
screen leaves a brief lingering shadow of itself where it had just been,
creating a kind of smear or blur. Lower quality computer screens often leave
ghosts. Technically, the secondary visual signal has been created and
received either earlier or later than the primary signal itself.
Ground Loop
This type of picture interference is caused when the ends of a video cable
have differing ground potential, causing an AC current. This is either a black
shadow bar onscreen or a tearing in the top corner of the picture results. The
use of ground loop insulators prevents this problem.
GUI (Graphical User Interface)
Pronounced ‘gooey’, this is the interface between the computer and the
matrix switcher. Active areas of the computer screen are programmable,
feature menus, icons, are clickable, and able to activate devices such as
VCRs and matrix switchers. Essentially, the GUI makes the CCTV system
easier to use.
A Hertz (Hz) is the unit used to measure frequency, with 1 Hz equal to 1
cycle per second.
Horizontal hum bars
Sometimes called Venetian blinds because they are horizontal bars (either
black or white) that extend across an entire picture. They’re either moving
or stationary, and are the result of roughly a 60 Hz interfering frequency
(usually from a 60 Hz AC power source).
Horizontal resolution
This measures the maximum amount of individual picture elements
recognizable in a single scanning line.
HTML (HyperText Markup Language)
HTML is the language used in the creation of WWW pages, with use of
hyperlinks and markup for text formatting.
HTTP (HyperText Transfer Protocol)
This is the protocol utilized to transmit and request information from WWW
servers to browsers, either online or over networks.
Networks rely on devices called hubs to connect multiple computers together
into a LAN. Standard hubs share the bandwidth across all ports (so an eight
port 100 Mps hub allocates this 100 Mps among the eight ports), while
switching hubs are able to give each individual port a dedicated bandwidth
amount (so these same eight ports could conceivably each receive a full 100
Mps of bandwidth on a switching hub).
Measured in ohms, impedance describes the input and output characteristic
of an electrical system. For the best signal quality, both input and output
impedances should be equal, with CCTV systems having 75-ohm impedance
Infrared camera
These cameras are well suited for surveillance of low light areas or areas with
no light at all. Infrared LEDs surround the lens and shine infrared light,
illuminating the scene. They usually have a fixed focal length lens, and
present b/w images during low light (though some offer color in the day and
b/w at night).
Infrared detector
This is an alarm that uses infrared light to detect nearby movement.
Infrared illuminator
A light source working in the infrared frequency range is called an infrared
Infrared radiation
Invisible to the human eye, this electromagnetic radiation has a wavelength
of greater than 750 manometers.
Insertion loss
If the inclusion of an electronic device into a line diminishes the signal’s
strength, it’s called insertion loss.
IP (Internet Protocol)
This is the protocol used to route a packet of data from source to destination
over the Internet. Every computer on the Internet has a different IP address
that identifies it from other computers.
IP address
This is a numeric address that is then translated into a domain name by the
DNS (domain name server). When we type in a website’s name, the
computer translates this into its IP address, which is a unique 32-bit
number. The TCP/IP protocol then uses it for routing the data packets to
their destinations. Each host has a unique IP address.
IP Camera (or Network Camera)
This signal from an IP camera is delivered over an IP network. The camera
digitizes the images, compresses them, and then sends them over the
network (if this sounds similar to a webcam, that’s because there is digital
webcam technology contained within a network camera). But a typical IP
network camera is much more advanced as compared to a consumer web
camera which needs to be attached to a computer to operate. IP enabled
security cameras usually offer a browser interface so that the user can
operate and view the video remotely over the Internet. A DVR system is
often comprised of an IP camera and a NVR.
The section of the lens adjusted to control how much light passes through it
and onto the CCD chip is called an iris.
ISDN (Integrated Services Digital Network)
ISDNs are digital telecommunications lines that transmit voice and digital
network services. Many telephone companies provide them, due to their
superior reliability and speed (up to 128K) over analog modems. The ISDN
standard improves compatibility for the integrated digital transmission of
voice, video, and data over normal copper telephone wires, which allows for
better quality and speeds. There are two primary types of ISDN: BRI (Basic
Rate Interface) and PRI (Primary Rate Interface). PRI is faster, with speeds
on par with T-1 circuits.
ITU (International Telecommunications Union)
Currently, 113 countries participate in the ITU, which is an agency of the
United Nations. Existent since 1865, the ITU is responsible for developing
international telecommunications for networked telecommunications. The
ITU-R is a subchapter, and is responsible for managing radio frequency
spectrum (including television and video) standards.
PTZ controllers utilize this stick as a control device for pan and tilt movement
of a PTZ security camera’s pan and tilt head.
JPEG (Joint Photographic Experts Group)
This is one of the most common file formats for compressed photo images. A
small amount of data, though not noticeable enough to be significant, is lost
in the compression process, making JPEGs a lossy compression algorithm.
LAN (Local Area Network)
A LAN is a high-speed network connecting computers that are nearby
(probably in the same building), and offers differing connection protocol
The speed of a network is dependent on both latency and bandwidth, with
latency referring to the time needed for an IP packet to travel from source to
destination. Wide bandwidth and low latency are preferable.
LED (Light Emitting Device)
Monochrome surveillance cameras use LEDs to provide infrared light. An LED
creates an infrared light frequency when stimulated by an electric charge.
This is the device responsible for focusing the image on the CCD, and most
offer adjustable focal length and aperture.
Level control
Level control is control of the main iris, and sets the auto-iris circuit to a
specific video level of the user’s choice. The iris is therefore set to maintain
this video level no matter what the light condition may be. A high level
opens the iris; a low level closes it.
Light sensor
Often used to turn infrared illuminators on or off, this device is triggered
when it detects a pre-set amount of light, and helps cope with low (or no)
level light conditions.
Limit switch
A security camera’s pan and tilt head with one of these devices installed
(either inside or outside it) is limited in the angles it can move.
Linux is an open source UNIX implementation, and a popular alternative to
the Windows operating system. It is often used in embedded operating
systems found in advanced Network IP Cameras. Linux is freeware.
A lumen (abbreviated as lm) is a unit that measures the visible power output
of a light. While watts measure the power the bulb needs, lumens measure
the visible light that the bulb generates.
Used more often than lumens when discussing security cameras, a lux is a
unit of illumination. It measures the amount of uniform light that falls on one
square meter (expressed in one lumen per square meter). Security camera
specs use the lux to indicate how much light they require to operate, with
lower lux levels indicating a camera as more effective in lower ambient light.
Look for 0.2 lux or less when choosing a low-light camera, and 2 lux or
higher for daylight cameras.
Matrix switcher
When a CCTV system needs to route one camera input to many monitor
outputs, it utilizes a device called a matrix switcher.
Mimic panel
This panel displays a site’s layout, including the location of surveillance
cameras. When the panel is interfaced with a switcher, it can be used to
switch any specific camera to the monitors.
Minimum scene illumination
This information (found on a camera’s data sheet) displays the minimum
light level the particular camera needs in order to provide an acceptable
monitor picture.
Even though it’s not as efficient as MPEG-4, the MJPEG is still an effective
way of creating video from the sequencing of JPEG images. The video from
store security cameras often uses this method when being formatted.
MOD (Minimum Object Distance)
This refers to the closest an object can be to the vertex of the lens and still
be in focus. The wider the lens angle, the smaller the MOD.
Monochrome means having a single color, or black and white for television.
Motion Detectors
These devices are used to detect motion on security cameras. Simple motion
detection triggers the camera to either record or set an alarm. Motion
detection by frame region instructs the camera to respond only if a certain
area of the screen/frame detects motion. Finally, advanced motion detection
analyzes the type of motion to see if it warrants alarm (such as crossing into
a secure area). One benefit of motion detectors is that cameras only record
when motion has been sensed, which saves disk space.
MPEG (Moving Picture Experts Group)
One of the most common coding standards for internet transferable video
images, the MPEG format is playable on nearly all free and payware video
players. MPEGs use lossy data compression. MPEGs first predict the initial
picture content, and then code differences between that and the copy, as
well as any extra information.
MPEG4 has a newer codec and supports 3D content, low bit rate encoding,
and support for Digital Rights Management, which controls the use of
copyrighted digital work. MPEG4 is used for web streaming media, broadcast
television, videophones, and CD distribution. MPEG-4 is widely used in video
surveillance, and has recently been improved to the AVC standard.
Multicast (or Multicasting)
This term refers to the Internet protocol that allows a single IP address (the
host) to send a packet to multiple destinations at once with a single, local
transmit operation. It also is used in video streaming to enable the
broadcasting of video to multiple recipients at once.
A video surveillance device with multiple video inputs and one video output is
called a multiplexer. Multiple security cameras are connected to it and their
images can be presented on one monitor. A front panel displays the buttons
that toggle each camera, and the signal from one camera or a combination
thereof can be displayed. Multiplexers are simpler to use as compared with
similar procedures on a DVR which normally requires a system login,
operating a keyboard and controlling a mouse.
Network Camera
Also known as a Network IP Camera, this is a stand-alone camera that uses a
standard web-browser to view live, full motion video from a computer
network, including over the Internet. They often feature an embedded OS
(operating system) and features like: FTP of images, web server capability,
and built-in motion detection.
NVR (Network Video Recorder)
Functionally similar to a DVR, a NVR also accepts IP camera inputs. NVRs
can be software based, making them suitable only for accepting IP camera
streams over the Internet.
These are units that measure the impedance or resistance of an electrical
Optical Filters
These filters selectively allow for different frequency light to pass through.
Outdoor Camera Housing
A protective shell for security cameras to be placed in outdoor environmental
conditions, these housings typically include cooling fans for summer use and
heaters for winter use. The heaters also eliminate fogging of the glass
anytime this occurs.
Outdoor Dome Housing
This housing is dome shaped for insertion of dome security cameras, is very
tamper resistant, and allows for PTZ.
This Pelco created protocol is used to control PTZ security camera movement.
A photon is the basic unit of light.
Pinhole Camera
Perfect for covert surveillance, this quarter sized camera is nearly impossible
to detect. With it’s small size comes limited abilities though, primarily a
small lens and limited zoom capabilities.
Pixel (Picture Element)
Pixels are the smallest possible display unit of visual information available for
building a graphical image. It is also the basic unit of a CCD chip, with most
CCD chips being comprised of over 300,000 pixels.
Power supply
Most security cameras utilize 24V AC or 12V DC power supplies. A power
supply is usually plugged into a regular electrical outlet or part of a
centralized power supply.
Since it scans all lines onscreen at once, 60 times per second, this type of
scanning is used by computer monitors to minimize flickering. It is also
better able to show movement, offering more detail and less ghosting than
interlaced scanning.
PTZ Camera
PTZ stands for Pan, Tilt, and Zoom. These cameras are usually remotely
controlled by software or a joystick. PTZ cameras are used when active real
time monitoring with the ability to point the camera’s viewing area to a
specific action or event is desired.
PTZ controller
The controller used to control PTZ camera movement, usually software or a
Utilizing digital video, this piece of equipment displays signals from four
surveillance cameras on one monitor.
A raster is a rectangular scan pattern of lines that the picture is created
upon. It also refers to an active TV monitor that has no video information
Real time video
Any picture having 24 or more frames per second appears continuous, or in
real time.
Reed switch
This type of alarm activating device becomes active when contact is either
opened or closed, as in a door or window being opened or closed. They are
also capable of switcher activation to activate the relevant security camera.
Regulated power supply
A DC power supply with a minimal ripple factor is considered to be regulated.
Remote monitoring
This allows an off site user to monitor surveillance camera feeds, so a user
can survey a site regardless of their location from it. The transfer of data
from camera to user can be either over the Internet or the Ethernet, with IP
cameras being suited to the task.
RF (Radio Frequency)
In order to be broadcast across a wireless network, video signals must be
modulated into a RF signal.
Having a thick center core, this type of coaxial cable is used to transmit video
signals of up to 550m.
More commonly used than RG-11 for CCTV, this coaxial cable transmits video
signals of up to 230m.
RGB (Red Green Blue)
These are the three primary colors of light. All other colors are derived from
their mixture.
A router is a piece of equipment facilitating the exchange of packets
throughout LAN or WAN networks. It moves packets across a predetermined
path to their destination by storing and forwarding the packets, and then
determining their optimal path along the network. A router is hardware
based, but can also include software.
RS232 (or RS-232)
This is the communication standard that applies to PC serial
communications. RS232 is commonly used as the mechanism for sending
instructions that control PTZ security camera movement.
RTP (Real-time Transport Protocol)
The Internet Engineering Task Force (IETF) developed RTPs to specify audio
and video signal management. It standardizes the packet formatting for
both for easy synchronization and Internet delivery. Streaming media
systems and video conferencing systems use RTP, while DVR systems rely on
this protocol in the implementation of the remote view feature. Since it
doesn’t specify how video surveillance playback is implemented, the data
from different RTP based surveillance systems usually cannot interoperate.
RTSP (Real Time Streaming Protocol)
This open standard for Internet streaming of audio and video is popular
among DVR makers for remote viewing of live or stored security camera
video over the Internet. RTSP controls the transmission of the data stream
much the way a television remote controls the television. Like RTP,
interoperability problems exist between different DVR systems.
Applied to the field of video surveillance, scanning is the panning of a camera
across the horizontal field of view.
Security Camera
The traditional CCTV camera is a multipurpose device capable of numerous
configurations and superb quality. They usually don’t include a lens, mount,
or enclosure. They also can be expensive to configure in comparison to
cameras designed for a specific purpose.
Sensitivity of a surveillance camera
This term refers to the minimum level of light the CCD chip needs to
generate an acceptable video picture, and is measured in lux.
Sequential switcher
A sequential switcher enables the simultaneous display or recording of
multiple surveillance cameras.
Shutter speed
This is the speed which the CCD chip can read out the charge. Using either
dipswitches or a surveillance camera’s menu (if one has been built in), the
default setting of 1/50 sec (PAL) or 1/60 sec (NTSC) can be increased up to
A type of multiplexer that allows you to simultaneously record images to tape
and display the live, full screen image of any individual security camera
(compare this to the duplex type which can also display multiple-picture
screen images while recording). A simplex multiplexer can display multiplepicture screen images, but it cannot record at the same time. Also unlike a
duplex multiplexer, it is unable to record and playback recorded tapes
SMS (Short Message Service)
Some of the more advanced Network cameras feature software that sends
notifications via the Cellular network to authorized users after programmed
events. Griffid is one example of SMS being implemented in network
surveillance software.
SMTP (Simple Mail Transfer Protocol)
This is the standard server-to-server protocol for the delivery of electronic
mail, either via Internet or on other TCP/IP networks.
SNR (Signal-to-Noise Ratio)
SNR measures the ratio between the usable video signal and noise or
Static IP address
This is an IP address that doesn’t change. Any computer can connect to it,
thereby making video surveillance systems with static IP addresses remotely
accessible from any location on the Internet.
Representing an improvement in quality over composite video, S-Video
separates chrominance and luminance onto two different signal wires,
resulting in better picture quality.
Frame formation in multi surveillance camera systems is started
simultaneously by the process of synchronization, and there are differing
ways this process can be achieved.
TBC (Time Base Corrector)
Multiplexers and quad splitters rely on a TBC circuit to align unsynchronized
video signal before the signal processing begins.
TCP/IP (Transmission Control Protocol/Internet Protocol)
These protocols enable communication between differing computer and
computer networks. The IP is a connectionless protocol that provides the
packet routing, while the TCP is connection based to provide reliability in
communication and multiplexing.
Telephoto lens
In order to make distant objects appear larger, cameras require a telephoto
Time lapse VCR
Used primarily by CCTV systems, this VCR enables increased recording time
on a videocassette by not recording all the frames.
Touch Screen
Advances in monitor technology have enabled touch sensitive monitors that
can perform specific actions by responding to a user touching relevant screen
A zoom lens that can stay in focus while zooming from wide angle to
telephoto position is said to be tracking.
UPS (Uninterruptible Power Supply)
Justifiably popular with many electronics users, a UPS stores electricity in a
battery and supplies power to a system (allowing a user to shut down w/out
losing data or continue for a specific time period) during a power failure.
URL (Uniform Resource Locator)
The URL is the Internet address that a software browser requires in order to
find that Internet resource.
UTP (Unshielded Twisted Pair)
This type of cable is used to transmit video signals across distances greater
than a coaxial cable can handle. The RG59 standard of UTP cable is roughly
600 ft. In conjunction with video baluns, they can stretch over 1200 ft. for
full color video. UDP is cost effective too, mainly due to lower costs than
coaxial cable, being easily terminated, and being capable to carrying data,
video, and audio signals across the same cable with little interference.
Variofocal lens
This type of lens has the capability of varying its focal length in order to
zoom in on images. An auto iris feature is required in order to achieve this.
Variofocal lenses are contrasted with fixed focal lenses, which are less
expensive and often allows more light to pass through them at their set
length, enabling better detection in low light circumstances.
Vertical resolution
The number of horizontal lines resolved in a picture is called the vertical
resolution, and is determined by the television scanning method, be it NTSC,
PAL, or some other format.
Vibration sensor
A device that activates when it detects vibrations in its detection zone, and
then activates a specific surveillance camera is known as a vibration sensor.
Video amplifier
This device boosts the strength of a video signal.
Video compression
This technique (often a MPEG format) compresses video into lower bit rates
for easier Internet transmission, often along narrower bandwidths. Video or
audio is compressed to shrink file size, ensuring acceptable transfer speed.
Compressed video can sometimes be of a noticeably lower quality, but still
clear enough to be useful. AVC is the successor to MPEG as the new video
compression standard.
Video distribution amplifier
This amplifier is able to boost signal strength and also to create multiple
video signal outputs.
Video intercom
Used at door entryways, this system utilizes audio and video for
communication or movement control of people.
Video server
This enables an analog camera to be converted into an IP camera, able to
stream digital video over an office network, phone, or ISDN connection.
Therefore, an analog based surveillance system can be upgraded and
networked to function as an IP surveillance system.
Video streaming
Streaming video delivers compressed multimedia content over the Internet in
a stream of packets. Viewers view the file as it downloads, instead of
downloading the entire file first. Streaming video first initializes the transfer,
and then buffers it. Bandwidth determines both picture quality and whether
or not the viewed video catches up with the downloading content, which
causes the video to stop. RealPlayer is one of the most popular free
streaming video players available. Video streaming is commonly used for
viewing live feeds from security cameras, with RTSP/RTP being the main
streaming technology currently in use.
WAN (Wide Area Network)
A WAN is a communications network serving a geographically large area
using satellite communications or telephone lines. The Internet is a WAN.
Network IP Cameras are capable of utilizing WAN systems.
Wavelength is how far an electro magnetic wave travels during one cycle.
When discussing DVR, the term refers to the color of light, which every color
having a different wavelength.
WDM (Wavelength Division Multiplexing)
This economical procedure enables data from different sources to be
simultaneously transmitted over the same fiber optic link. It achieves this by
assigning a unique wavelength to each data channel, resulting in many
possible wavelengths traveling across one link, which allows one fiber link to
do the same work as two or more.
Webcams are cameras that connect to the Internet, either via PC or directly,
and that allow remote user access. An IP camera is a popular webcam for
video surveillance that does not need a PC connection.
White balance
CCD security cameras feature this adjustment to compensate for ambient
light color. Since there’s a color difference between standard light bulb light
and sunlight, white balance adjusts to ensure a more realistic picture. This
feature may be set by manual adjustment, or it may have preset settings for
the most common situations.
Wide angle lens
This lens enables a wide view of the scene, with a magnification ratio less
than 1.
The wireless transmission of video signals can be carried out over both short
and long ranges, with 2.4 to 5 GHz devices for short distances and highpower line dedicated site solutions for several miles or more.
Zoom lens
A zoom lens has the advantage of offering a variable focal length to view
both wide angle to telephoto scenes.
Zoom ratio
This measures the ratio between the maximum and minimum focal length
that a zoom length is capable of.
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