Glossary Of Video Surveillance Terms
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A Glossary of Video Surveillance Terms and Definitions – the Path to Security and Knowledge

From the smallest business to the largest corporation, chances are they all rely on some form of video surveillance to keep their workplace secure. With so many advances in the video surveillance field and affordable options to choose from, finding the perfect system to suit your specific needs can seem confusing. With our guide however, it has never been easier. This comprehensive glossary arms you with the necessary knowledge to successfully carry out your search and make the right consumer choices.

  • Activity Detection
    Mutliplexers use this feature, which is a video motion detection technique, to give relay closure for alarms and to improve the update times of video cameras.
  • Backlash
    Backlash (measured in degrees) is when a camera’s Pan Tilt head cannot stop instantaneously, and is usually caused by excessive looseness in gears, pulleys, or other parts. Pre set PTZ surveillance cameras are rendered ineffectual by Backlash.
  • 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.
  • 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.
    CODEC means compressor/decompressor and is any technology used to compress and decompress data. It converts analogue input into digital, and then converts it back to analogue. CODECS can be either software applications or hardware components, or both. DVRs use codecs to compress video streams from security cameras, and then store this compressed data on a hard disk.
  • 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.
  • De-multiplexing
    This refers to the procedure of separating different channels of video, audio, or data that were multiplexed at the source.
  • 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.
  • 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).
  • 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.
  • 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.
  • 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.
  • 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.
  • 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 illuminator.
  • Infrared radiation
    Invisible to the human eye, this electromagnetic radiation has a wavelength of greater than 750 manometers.
  • 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.
  • 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.
  • 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.
  • 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.
  • Multiplexer
    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.
  • Pelco-D
    This Pelco created protocol is used to control PTZ security camera movement.
  • 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.
  • PoE (Power over Ethernet)
    This abbreviation refers to a method of supplying power to an IP camera using Category 5 Ethernet cables over a physically wired LAN network.
  • Polarizer
    This filter eliminates light reflected from glass, water, and other surfaces, thereby minimizing unwanted visual glare affects from glass and other non-metallic surfaces.
  • Post-Record
    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.
  • Pre-Record
    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.
  • 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.
  • Quad
    Utilizing digital video, this piece of equipment displays signals from four surveillance cameras on one monitor.
  • 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.
  • 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.
  • SAD (Sum of Absolute Difference)
    This acronym refers to a mathematical technique used in motion detection.
  • 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.
  • Sequential switcher
    A sequential switcher enables the simultaneous display or recording of multiple surveillance cameras.
  • Simplex
    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.
  • 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 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.
  • S-Video
    Representing an improvement in quality over composite video, S-Video separates chrominance and luminance onto two different signal wires, resulting in better picture quality.
  • Time lapse VCR
    Used primarily by CCTV systems, this VCR enables increased recording time on a videocassette by not recording all the frames.
  • 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 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.
  • Webcam
    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.
  • Wireless
    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.
  • Y/C
    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.
  • 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.
  • There you have it -- 58 terms, numerous choices, and a wealth of information. If you keep this guide handy during your search, you’ll find that zeroing in on the most appropriate system options will be that much easier. It need only be a matter of days until your personal or business site offers the surveillance capabilities you desire.

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    About the Author

    Ben Davidson is an experienced freelance writer of technological subjects. His work provides clear and valuable information about video security, CCTV cameras, and CCTV systems for consumers looking to make purchases for their home or businesses.

    This article on the "The History of Video Surveillance" reprinted with permission.

    Copyright © 2004-2005 Evaluseek Publishing.

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