CCTV Glossary of Terms

Welcome to the webs largest CCTV Glossary of Terms and Definitions. Below you will find links to the most common terms used in CCTV. The links will take you to the most detailed definitions and explanations found in any CCTV Glossary of Terms.

Get Free Video Surveillance Systems Quotes!

Special Report!

How to Choose the Right Security Camera 2nd Edition

The comprehensive guide has a strong focus on IP Technology.  Get your free download now!

Expanded with additional quick view charts, updated selection survey and mounting examples.

Enter your name and email below and we will send it right over!

Have a Question?

Please note that all fields followed by an asterisk must be filled in.

You can scroll thru the list to find what you are looking for or just use the Ctrl-F function in your browser to search for the specific term you want.

This CCTV Glossary of Terms is being updated on a regular basis so it would be a great idea to bookmark it and check back often.

If there is not definition below the term you can click the term to view the terms definition page.

Access Card

Access Code

Access Point


AGC Automatic Gain Control

Alarm Input


Ambient Light Level

Analog Signal

Angle of View



Address Resolution Protocol

Aspect Ratio

Aspherical Lens


Automatic Gain Control (AGC)

Auto Iris (AI)

Auto Iris Lens

Automatic White Balance

Back Focus





Back Light Compensation BLC

BNC Connector


Bullet Camera


Cable Tray

CCD Charge Coupled Device

CCTV (Closed Circuit Television)

CIF (Common Intermediate Format)Resolution



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 carrier.


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.


In a multiplex signal, video, audio, or data channels with adjacent signal frequencies can create interference. This interference produces a noise known as crosstalk.

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 movement.

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.

D1 Resolution

Day/Night Camera

A camera that is 'Day/Night' means it can capture video in both day and nighttime. In low light conditions, the Sony Day/Night chipset switches from color to black & white at night to enhance the picture quality

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.

DC Type Lens

An auto-iris lens with internal circuit that receives voltage and a video signal from the camera to adjust the iris.

DD (Direct Drive)

This uses a gearless drive mechanism, making it less prone to mechanical failure. PTZ security cameras will often use them for pan, tilt, and zooming.

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

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 connection.

Digital Signal

A sequence of binary bits that represent ones and zeros makes up a digital signal.

Digital Signal Process

A sophisticated chip in the camera that will enhance and compress the image before it is either converted to analog and transported or remains 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.

Duplex (Multiplexer)

A multiplexer that allows the user to look at multi-screen images while performing time multiplex recording.


DivXNetworks 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 20ígigabyte hard drive.

DNS (Domain Name Service)

DNS is the system that matches server IP addresses to web site domain names.

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.

Dummy Camera

Dummy Cameras is simply a security camera housing that has no actualy internal working part. The camera may include a red led light that may be powered to have the apperance that it is on and recording. Dummy cameras along with signs that say the area is under surveilance may be used to preempt any one who would want to commit a crime from doing so because of the possible threat of being captured on video. Dummy Cameras can come in a variety of different sizes, colors, etc.


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 Internet.

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.

EI (Electronic Iris)

Automatically changes a CCD cameraís shutter to mimic Auto Iris control, allowing fixed or manual iris lenses to be used in a range of areas that used to require an auto iris lens.

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 recorders.

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.

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 users.

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.

Extruded aluminum

This type of aluminum is used to construct housings for CCTV (closed circuit television) applications and provides the added benefits of increased strength, durability and resistance to harsher environmental conditions as compared to plastics.

Fast Lens

FCC (Federal Communications Commission)

This United States commission regulates communications by setting rates, controlling broadcast licensing, and testing electronic equipment to RF (radio frequency) transmission and related standards.

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.

Fixed Iris

Fiber Optics

These high-speed computer-networking cables transmit data using light instead of copper.


Field of View


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.

Flange back

This refers to the distance from lens flange (the beginning of the lens mount) to the focal plane. The flange back measurement for C-mount lenses is 17.52mm, while CS-mount is 12.5mm.

Flickerless Mode

Setting in cameras that will allow the camera to work with 50hz fluorescent lights to keep the camera from pulsing


Focal Length


It is the light intensity (illumination) of a surface one foot distant from a source of one candela. It is equal to one lumen per square foot. (1FC = 1 lm ft2). The footcandle is the unit used to measure incident light.

Frames Per Second FPS


Frames Rate

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 .45 to 1.


The use of composite video, composite sync, or vertical or horizontal sync to synchronize one or more cameras is known as Gen-lock.


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.

H.264 Compression


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. Theyíre 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).


Image intensifier

This device is used to intensify low-level lighting conditions via light sensitive phosphor screens, and is specifically used to improve the performance of surveillance cameras in low light conditions.

Image Size see CCTV Resolution

Images Per Second IPS


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 throughout.

Index of refraction

This ratio measures the angle of incidence to the angle of refraction of light, with a denser medium bending more light and having a higher index of refraction.

Infrared Camera

Infrared detector

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 Illuminator

Infrared radiation

Injection molded plastic

Smoked or tinted plastic (but still translucent) is melted into a liquid from pellets and injected into a "dome-shaped" mold to construct security camera dome housings.

Insertion loss

If the inclusion of an electronic device into a line diminishes the signal's strength, it is called insertion loss.


This refers to a type of display where the electron beams alternate between scanning the even numbered lines and then the odd numbered lines, resulting in the two vertical scans on the screen, with the field (each set of lines) being updates 60 times a second, and with the frame (both fields) updated 30 times a second.


Some alarms and security systems use the process of interleaving to add extra frames from alarmed cameras to a time multiplexed sequence while the alarm is activated. This prioritizes the view from alarmed cameras in the sequence of camera views.

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 websiteís 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 is 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.

IP Ratings

IR Cut Filter

An IR Cut Filter is an extra filter inside the camera that moves behind the camera lens when it gets dark. A camera with an IR Cut Filter will produce very high quality images in low light conditions.


Units on the scale defined by the Institue of Radio Engineers. IRE 40 would be the amount of useable video in a low light situation. IRE 100 would be fully useable video. It is generally stated on a camera spec sheet next to the LUX level.

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)


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)

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 options.


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 Diode)

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.

Loss Prevention

Best summarized as "not having anything stolen", loss prevention is the practice of securing devices or information from theft or loss. Video surveillance is a common practice in preventing theft or other losses of property like vandalism.



Manual Iris

Matrix switcher

When a CCTV system needs to route one camera input to many monitor outputs, it utilizes a device called a matrix switcher.

Megapixel Cameras

Megapixel Resolution

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.


MMS (Microsoft Media Services)

MMS is the first streaming protocol created for the Microsoft Windows Media Player.

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.

Motion Detection

Recording method for digital surveillance systems. When someone walks in front of a camera, the pixels change and the DVR defines this as motion. The surveillance system will then record these images to the hard disk. This is a popular recording setup as every event recorded is actually motion driven as opposed to a static image if the system was set to record 'round-the-clock'.

MPEG (Moving Picture Experts Group)


MTBF (Mean Time Between Failures)

MTBF measures the average time that a device works properly without failure; unfortunately, it is usually measured in hours. An hour measurement does not translate well to the average consumer looking for life expectancy in years.

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. A small part of a monitor's viewing area (1/16th the screen area) is called a cameo. Multiplexers create multiple analog signals from security cameras and then combine them into multiple cameos on the screen, which enables simultaneous viewing of up to sixteen different camera pictures

Nema Ratings

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.

Neutral Density Filter (N/D)

This category of lens filter reduces light of all wavelengths in equal amounts. NTSC (National Television Standards Committee) The NTSC represents the American and Japanese standard television video signal format of 525 picture lines and a 60Hz field frequency.


Random spurts of electrical energy or interference.


National Television Systems Committee that worked with the FCC in formulating the standards for the United States color television system.

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 device.

Optical Filters

These filters selectively allow for different frequency light to pass through.


This troubleshooting device translates electrical signals into voltage versus time based waveforms that are displayed onscreen, allowing visual feedback when adjusting CCTV components.

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. See IP Rating.

Outdoor Dome Housing

This housing is dome shaped for insertion of dome security cameras, is very tamper resistant, and allows for PTZ.

PAL (Phase Alternating Line)

Europe's television video signal standard is known as PAL. PAL uses 625 picture lines and a 50Hz field frequency, and is incompatible with NTSC.


If a system component is non-powered, it is considered passive.


These storage devices resemble a credit card and are typically used to expand the hardware functionality of portable devices such as laptops. In video surveillance application, PCMCIA cards can be used with portable PCs to add real-time full motion video capture of live security video. When used with digital cameras, they provide portable storage and a method for saving and transferring photos between digital cameras and PCs.

Peak to peak

Video Signal measurement from the base of the Sync pulse to the top of the white level. A full video signal should be one volt.


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.

Pixim Cameras

Power Over Ethernet (PoE)

This abbreviation refers to a method of supplying power to an IP camera using Category 5 Ethernet cables over a physically wired LAN network. This is often used with the installation of IP Cameras saving time/money by reducing cabling.


This filter eliminates light reflected from glass, water, and other surfaces, thereby minimizing unwanted visual glare affects from glass and other non-metallic surfaces.


Sometimes referred to as post-record time, this is a DVR's ability to record after a motion detection event has occurred. It records for a specified amount of time after the event has been triggered, even though the motion may have ceased.


This device measures voltage or a potential voltage difference by comparing it with a standard voltage. It can also change resistance by moving the contact point, and is used to record pre-set positions in both zoom lenses and pan tilt heads.

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.

PPP (Point-to-Point Protocol)

Point-to-point Protocol is the primary method used in establishing a direct connection between two devices on a network (usually a computer and the Internet). It is a communication protocol between computers using one of several methods: usually TCP/IP, telephone lines, or ISDN.


This DVR capability will record video prior to motion being detected, then send to the disk as much prior video as memory allows and video of the motion itself.

Pressure mat

Placed before doorways, gates, and other entrances, this device responds to pressure (usually being walked or stood upon) to either open doors or activate the surveillance camera trained on that area.


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.


Protocols are standard procedures used for regulating data transmission between computers. Protocols exist to minimize errors during the exchange of data.

PTZ Camera

PTZ controller

The controller used to control PTZ camera movement, usually software or a joystick

QCIF see Resolution

This resolution is one quarter of CIF, with 144 lines and 176 pixels per line.

Quad Splitter

Utilizing digital video, this piece of equipment displays signals from four surveillance cameras on one monitor.

Range finder

This is a device that determines the required focal length and the resulting monitor image. While looking through it, the user can adjust the range finder to get the optimal image, with numbers on the range finder displaying the needed focal length.


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 displayed.

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.

Reflected Light

The scene brightness or the light being reflected from a scene. Usually it represents 5 to 95 percent of the incident light, and it is expressed in foot-lamberts.

Regulated power supply

A DC power supply with a minimal ripple factor is considered to be regulated. Remote head surveillance camera For surveillance situations where space is limited, this type of camera separates the CCD chip from the camera body by cable, considerably shrinking the overall camera size.

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 which is approximately 1800 ft.


More commonly used than RG-11 for CCTV, this coaxial cable transmits video signals of up to 230m which is approximately 800 ft.

RGB (Red Green Blue)

These are the three primary colors of light. All other colors are derived from their mixture.

Ripple factor

Too little filtering in a DC power supply creates an amplitude variation called the ripple factor; with large amounts of it able to damage DC powered surveillance cameras.

ROI (Region of Interest)

Applied to the field of video surveillance, ROI stands for Region of Interest, meaning an area of the frame where motion is detected, in turn activating the surveillance camera.


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 doesnít 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.

SAD (Sum of Absolute Difference)

This acronym refers to a mathematical technique used in motion detection.


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 donít 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 1/100,000.


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 multiple-picture screen images, but it cannot record at the same time. Also unlike a duplex multiplexer, it is unable to record and playback recorded tapes simultaneously.

Signal to Noise Ratio (S/N)

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

Spot Cam

Spot Cams are effective security cameras, useful for general surveillance needs. They are intended to be operable out of the box (mounting bracket often not included), and most have their own integrated varifocal lens. Be certain to choose a Spot Cam with its own auto iris feature and day/night capability.

Static IP address

This is an IP address that doesnít 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.

Sync generator

This piece of equipment generates sync pulses that are used for the synchronization of surveillance cameras.


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.


Control of PTZ cameras is provided using Telemetry Control. This signal is sent down 'twisted pair' cable or along the same coaxial cable the video signal is being sent down. Typical Telemetry signals are RS-485 or RS-422.

Telephoto lens

In order to make distant objects appear larger, cameras require a telephoto lens.

Test Pattern Generator

When adjusting and testing a monitor, a test pattern generator is used to create a test pattern for the required visual feedback. This device can also create a test pattern that can be used to verify the integrity and possibly troubleshoot the source video signal.

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 areas.


A zoom lens that can stay in focus while zooming from wide angle to telephoto position is said to be tracking.

UDP (User Datagram Protocol)

UDP is a communications protocol that makes possible the sending of datagram messages from one computer to an application in another computer. Itís connectionless and suffers from unreliability, since it is unable to check for any errors in delivery. UDP is often a protocol used in video streaming because it ignores lost data and continues the live feed of information (this being preferable to the interruption of real-time data while attempting to retransmit lost data).

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 800 ft. In conjunction with video baluns, they can stretch over 1200 ft. for full color video. UTP is cost effective too, mainly due to lower costs than coaxial cable, being easily terminated, and being capable of carrying data, video, and audio signals across the same cable with little interference.

Varifocal Lens

Vertical resolution

The number of horizontal lines resolved in a picture is called the vertical resolution, and is determined by the television scanning method in north America of NTSC.

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 Splitter

CCTV device that splits the video signal from a camera (or cameras) so it can be used more than once.

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.

Video surveillance

This term refers to the use of CCTV and DVR to monitor secure sites, or portions thereof. Video Surveillance systems can start with a few as one camera. For systems using more than 16 cameras, enterprise video surveillance systems are preferable. The many terms defined in this glossary give an idea of the many options available for different security needs and situations. In today's professional world, Video Surveillance (often referred to as CCTV) is the most cost effective way to achieve loss prevention.

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.


This type of image compression is mainly used for single images and not video streams. Because it is superior to JPEG compression, it is however used in some video surveillance codecs, though there is not a universally adopted standard for usage of this codec.

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.

WDR Wide Dynamic Range


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 thereís 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.

Wide Dynamic Range WDR


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 high-power line dedicated site solutions for several miles or more.


Occasionally known as s-video, this video signal splits chrominance (c) and luminance (y) onto two separate signal wires for better composite video picture quality.

YIQ (Luminance In-Phase Quadrature)

The color space used in NTSC is called the YIQ.

YUV (Luminance Chrominance)

YUV is the color space used in PAL, and is preferred for video signals. YUV and RGB can be converted back and forth.

Zoom lens

A zoom lens has the advantage of offering a variable focal length to view both wide angle to telephoto scenes and keep them in focus.

Zoom ratio

This measures the ratio between the maximum and minimum focal length that a zoom length is capable of.

New! Comments

Leave your comments in the box below.
Share this page:
Enjoy this page? Please pay it forward. Here's how...

Would you prefer to share this page with others by linking to it?

  1. Click on the HTML link code below.
  2. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.

Get FREE home security quotes now!

Just fill in the form below.