Activity Detection: A feature of the Generation 3 video multiplexer range that uses video motion detection techniques to improve the camera update times. It also gives a relay closure.

AFC (Automatic Frequency Control): An electronic circuit used whereby the frequency of an oscillator is automatically maintained within specified limits.

AGC (Automatic Gain Control): Circuitry in a surveillance camera which boosts the video signal (including the noise). It becomes operational when the light level is low.

Alarming: The ability of CCTV equipment to respond to an input signal, normally a simple switch closure. The response varies depending on equipment type, most common is for switcher to ‘hold’ on the camera corresponding to the alarm input.

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 (PIR) for motion detection. Alarm inputs can be self powered or can require external power (usually 12V).

ALC (Automatic Level Control): On AI lenses, also known as the peak/average control. Adjusting this control allows the auto iris circuitry to either take bright spots more into consideration (peak), bringing out detail in bright areas, or less into consideration (average) bringing out.

Algorithms: Its general definition means a set of mathematical instructions to solve a task. In the field of cctv (close circuit television) & video technology, they enable digital compression of the video picture.

Ambien Light Level: This is the amount of background light present at any specific time.

Analog:  A signal in which any level is represented by a directly proportional voltage; not digital.

Angle Of View: Represents the area of the scene (maximum horizontal and vertical angle) that can be seen through a lens. It is measured in degrees.

Aperture: The lens opening that controls the amount of light reaching the pickup device (imager).

Aspect Ratio: The ratio of the picture frame width to the picture frame height in standard TV systems. The aspect ration for NTSC and PAL is 4:3, It is 4 units horizontal over 3 units vertical.

Aspherical Lens: A lens designed with a non spherical shape so that it refracts the light passing through it to either lower the lens aperture so that it passes more light or decreases barrel distortion on wide angle lenses.

Attenuation: A decrease or loss in a signal. Reduction of signal magnitude (loss) normally measured in decibels.

Auto Iris Lens: A lens in which the aperture automatically opens or closes to maintain proper light levels on the cameras pickup device.

Automatic pan: A feature of a pan/tilt or pan only head which allows the head to continuously move (pan) left and right between two fixed points. These fixed points can be set by adjusting the limit switches in the head.

Auto Terminating: Feature whereby the equipment automatically selects the correct termination depending on whether the video output BNC is connected.

Auto White Balance: Feature on color cameras whereby the camera constantly monitors the light and adjusts its color to maintain white areas.

Back Focus: The mechanical aligning of the imaging device with the focal point of the lens. Most important on zoom lenses to ensure the image stays in focus throughout the zoom range.

Balanced Signal: Method of transmitting video, usually over twisted pair cable, that consists of two equal but opposite signals being sent down two conductors.

 Band Width: The frequency range of a signal. The span that the information-bearing signal occupies or requires or the difference between the lowest and highest frequency of a band.

 Base-Band Video: Unmodulated video signal suitable for display on a monitor but not a domestic TV.

 Black Level: The level of the video signal that corresponds to the maximum limits of the black areas of the picture.

 Blanking (Field And Line Flyback Blanking): The operation of turning off the monitor display, or pick-up device, during sync pulses to avoid thin white lines appearing on the picture.

 BLC (Back Light Compensation): A feature of modern CCD cameras which electronically compensates for high background lighting to give detail which would normally be silhouetted. With backlight scene, the auto iris function responds to the bright portion of the screen, thus causing the iris to narrow and resulting in the "darkening of the subject" phenomenon. Backlight compensation is a function that can be utilized to correct this phenomenon.

 BNC: A type of video connector used to interconnect two coaxial cables or connect a cable with other cctv (closed circuit television) components, the most commonly used connector in CCTV.


 C Mount / CS Mount: The two industry standards for mounting a lens on a camera. The C-Mount lens has a 17.5mm flange back distance. The CS-Mount lens has a 12.5mm flange back distance.

Camera: A device that translates light into a video image and transmits that image to a monitor for viewing. It contains the image sensor and other electronic circuitry to create a video signal.

Category 5: This refers to the quality assurance of connection parts such as unshielded twisted pair (UTP) cables and connectors. With LAN, category 3 is primarily utilized. For 100 BASE-TX, category 5 and above are used, and category 5e and above are required for 1,000 BASE-T.

 CATV: Short for Cable Access Television. The method for distributing RF signals via coaxial cable rather than radiated through the air.

 CCD: Charged Coupled Device. This is a solid state semiconductor imaging device often referred to as an integrated circuit, chip or "imager." Solid state cameras are sometimes referred to as CCD cameras.

 CCIR: The European TV standard 625 lines 50 fields.

 CCTV: The common abbreviation for Closed Circuit Television. A private or closed television system.

CD-RW: A CD-ROM that can be written, erased, and rewritten by a CD-RW drive.

Central Processing (On-line processing): A system where all systems information is stored in a central location and all go or no-go decisions are made by this unit.

CF (Compact Flash): This is the standard for memory cards advocated by San Disk Corporation, and is utilized as a storage device for digital cameras etc. Compact Flash combines flash memory that does not go off even when the power is turned off and an I/0 controller circuit on just one card.

Chrominance (C): The part of the video signal corresponding to the color information.

CIF (Common Intermediate Format): This is the universal video signal format regulated by ITU-T H.261. CIF supports moving Images with a data rate of up to 30 frames per second and a resolution of 352 x 288 pixels.

Coaxial Cable: A type of shielded cable capable of carrying a wide range of frequencies with very low signal loss.

Composite Video: The complete video signal consisting of the video information, the sync pulse and threshold reference signal.

Contrast: The range of light and dark values in a picture or the ratio between the maximum and the minimum brightness values.

Crosstalk: An undesired signal that interferes with the desired signal.

CRT (Cathode Ray Tube): The picture tube in a video monitor that can reproduce the picture image seen by the camera.


 Db (Decibel): A measure of the power ratio of two signals. It is equal to ten times the logarithm of the ratio of the two the iris.

DC Type Lens: An auto-iris lens with internal circuit which receives voltage and a video signal from the camera to adjust signals.

Depth Of Field: The area in focus in front of and behind the subject.

Digital: A signal that levels are represented by binary numbers. These can be kept in a store.

Digital Recording: This is the latest form of recording and is relatively new to the CCTV industry as a result is not the most economical method however it does have several advantages over the VCR analogue tape recorders. First of all it enables quick access to the desired.

Distribution Amplifier: A device that accepts a video signal and sends it out over a number of independent outputs.

DNS (Domain Name System): This system is used to replace IP addresses, which are expressed on the internet with numerals (e.g., with domain names that are easy to remember. On the internet there are servers referred to as DNS servers that have IP address and domain name tables.

DSP (Digital Signal Processor): This processor converts the input analog signal to a digital signal and then performs a variety of signal processing tasks. Thus, unlike analog processing, it is possible to produce stable and clear images without signal degradation within the circuit.

Duplex (Multiplexer): A multiplexer with two frame stores allowing it to show multi-screen pictures while performing time multiplex recording.

Dwell Time: The length of time a switcher displays one camera before sequencing to the next. Usually a variable setting.

Dynamic IP Address: A Dynamic IP address is a type of account from an ISP (internet service provider) where your computer or network is assigned an IP address that constantly changing and never remains the same. Also see IP Address and Static IP.

Dynamic Range: This refers to the range within which the reproduction of images can be performed without adversely affecting gradation. The amount of light necessary for the luminance signal to reach the white peak at 100lRE (of the amount of light with which it is possible to perform the reproduction of images without clipping even when more light comes in than the amount stated above.

EI (Electronic Iris) Shutter: Electronic Iris shuttering is the ability of the camera to compensate for moderate light changes in indoor applications without the use of auto iris lenses.

EIA (Electronic Industry Association): US TV standard 525 lines 60 fields.

Electronic Zoom: This is a function that employs the scanning variable of an image device or image memory rather than an optic lens to electronically enlarge or shrink the Image on the screen.

Ethernet: This is the LAN standard devised by Xerox Corporation, DEC Corporation and Intel Corporation, and has been standardized by the IEEES02.3. CSMA / CD has been adopted for data transmission over networks.

Equalization: The process of correcting losses of certain components in a signal.

Event recorder: A type of recorder that is normally maintained in pause mode and starts recording only when activated by an alarm.

 Ext. Sync (External Sync): The ability of CCTV equipment, normally cameras, to accept one or more of the standard sync formats so as to align itself to the rest of the system.

Fail safe: Is a locking device that is unlocked when no power is applied.

Fail Secure: Is a locking device that is locked when no power is applied. These are not normally used for exit doors since they cannot be unlocked during a power outage.

FC (Foot Candle): A measurement of light. 1 lumen per square foot.

Fiber Optic: The process of transmitting light through a long, flexible fiber such as glass or plastic, for the purpose of transmitting video, audio, or data over long distances.

Field: One half of a frame of video and consists of 312.5 (PAL) and 262.5 (NTSC) scan lines. Odd and even fields are combined to form a single frame

Field Of View: The maximum viewed image (area covered) a lens "sees." The horizontal or vertical scene size at a given distance from the camera.

Fixed lens: A lens with a fixed focal length. A wide range of fixed lens are available to suit different applications e.g. 2.6mm, 4.8mm, 8mm, 16mm, 25mm, 75mm etc.

Flange Back: The distance from the flange of the lens (beginning of the lens mount) to the focal plane. C-mount lenses have a flange back distance of 17.526mm vs. 12.5mm for CS-mount.

Firewall: This is a software system that is used to prevent unauthorized entry into an organization's computer network from the outside. It also refers to computers with built-in firewall systems.

Focal Length: The distance (in millimeters) from the lens to the surface of the image sensor. The shorter the distance, the wider the view; the longer the distance, the narrower (telephoto) the view.

Focus: The focal point. An adjustment to the lens optics to improve the clarity of the picture.

Format: The size of the cameras pickup device (imager). Current standard formats are 1/4", 1/3" and 1/2".

Frame: The basic unit of a moving picture. The frame consists of two fields of video information. A complete picture / frame contains 625 scan lines (PAL) or 525 scan lines (NTSC).

Frame Store: An electronic device used to capture and digitally store a video image. It can be an independent unit or in built in other equipment like fast scan video transmitters or video motion detectors.

Frame Rate: This rate is established by V.Networks and refers to the number of frames transmitted per second for JPEG and MPEG 4 Images. The maximum frame rate is fixed for each image size depending on the specifications of the respective V.Networks models.

F-Stop: A term used to indicate the speed of a lens. The smaller the f-number, the greater is the amount of light passing through the lens.

FTP (File Transfer Protocol): This is one of the communications protocols used when exchanging files over the internet. FTP is employed as the standard internet fiIe transfer method. Selecting FTP can often save time when downloading.

Genlock: To synchronize one piece of equipment to the sync pulses of another. This is a type of external sync system with a function that synchronizes external sync signals with frequency and phase. There are three types of genlock input signals: composite sync signals (composite SYNC), composite video signals (VBS or VS) and Black Burst Signals (BBS).

 Ghost: A shadowy or weak image in the received picture, offset to either the right or to the left of the primary image.

 Gigabyte (GB): 1,024 megabytes or 1 billion characters of information. Also see Megabyte.

 Gray Scale: The number of variations from white to gray to black.

 Ground: An electrical connection point that is common to either a metal chassis, a terminal, or a ground bus.

Ground Loop: Effects video pictures in the form of a black shadow bar across the screen or as tearing in the top corner of a picture. Caused by different earth potentials in a system.

 Ground loop current: An AC current produced in a video cable when the two ends of the cable do not have the same ground potential.

Ground loop insulator: An isolation transformer which can eliminate ground loop currents by removing any direct connection between the inputs and outputs

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 (also known as AVC [Advanced Video Coding] and MPEG-4): This is a standard for video compression. H.264 is a block-oriented motion-compensation-based codec standard. The H.264 standard and the MPEG-4 AVC standard are jointly maintained so that they have identical technical content.

Half Duplex: This is a transmission method by which data cannot be sent and received simultaneously, but rather can only be transmitted in one direction at a time.

Hardwired: Method of controlling camera points using multi-core cable.

Horizontal Resolution: The maximum number of individual picture elements that can be distinguished in a single scanning line.

HTTP (Hyper Text Transfer Protocol): This is a protocol used by World Wide Web (WWW) servers and Web browsers for sending and receiving information such as files.

Hub: 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).

Hz (Hertz): A unit for measuring frequency. 1 Hertz = 1 cycle per second. 


 Illuminance: The amount of luminous flux falling on a surface area and is measured in lux or foot candle.

Image Burn (Retained Image): A change produced in or on the target of the pickup device which remains after the removal of a previously stationary light image.

Image Device (Imager): The detector in the camera, either a tube or a CCD solid state device.

Impedance: The effective resistance of an electronic circuit to an A.C. signal. The input and output characteristic of any electrical system and is measured in ohms. For maximum signal transfer, the input and output impedance should be the same. cctv (closed circuit television) systems have a 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.

Infrared Illumination: When a “low-light” is subject to dark conditions, active infrared illumination must be applied for best results. Active infrared illumination is a new surveillance technology that is so effective that the images produced are often mistaken for regular daytime monochrome images.

Insertion Loss: The signal strength loss that occurs when a piece of equipment is inserted into a line.

Intensifier: An electronic device that creates an output image brighter than the input (original) image. Optical amplifier.

Interference: When attached to a security camera, an alarm input provides enhanced security in External energy which interferes with an electrical signal causing picture distortions.

Interlace: A scanning process where every other horizontal line is scanned in one field while the alternate lines are scanned in the next field to produce a complete picture frame.

Interleaving: 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.

Internal Sync (Crystal Controlled): A camera that generates its sync pulses without reference to any other source. Normally using a crystal controlled oscillator.

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: The Internet Protocol address; a unique numeric address such as Also see Static IP and Dynamic IP.  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 (Ingress Protection) Ratings: Standard for measuring the protective ability of outdoor enclosures that are used in video security, The IP Code (or International Protection Rating, sometimes also interpreted as Ingress Protection Rating) was developed in Europe. (Ingress means enter in. 

The First digit indicates the level of protection that the enclosure provides against access to hazardous parts (e.g., electrical conductors, moving parts) and the ingress of solid foreign objects. Second digit indicates the level of protection of the equipment inside the enclosure against harmful ingress of water.