| Word | Description |
| A.I. (Auto Iris) | An electronic circuit fitted to the iris of a lens to help compensate for large changes in light levels. |
| A.L.C. (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 detail in shadows. |
| AC (Alternating Current) | An alternating current is an electric current whose direction reerses cyclically, as opposed to direct current (DC), whose direction remains constant. The usual waveform of an AC power circuit is a sine wave, as this results in the most efficient transmission of energy. Used generically, AC refers to the form in which electricity is delivered to businesses and homes. |
| ADSL | Asymmetric Digital Subscriber Line |
| ADSL (Asymmetrical Digital Subscriber Line) | A telephone line with uneven transmission rates; half the transmission can attain speeds up to 640 kbps; the other half can attain speeds of 2.048 Mbps or greater in the opposite direction. |
| AGC (Automatic Gain Control) | An electronic circuit that tries to keep signals at a constant level; more useful in cameras at low light levels. The higher the number the better, typical values 12 - 20dB i.e. a gain of approx 4x - 10x. |
| Ah | Ampere hours. e.g. 1A for 6 hours = 6Ah. Always de-rate the battery capacity by 66% |
| 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. |
| Ambient Light Level | Background or general light level of a given area. |
| Analogue | A signal in which any level is represented by a directly proportional voltage; not digital. |
| Angle of View | This is what alters (not the focal length) when you use a lens designed for one format on another format. It decreases with format size. |
| Aperture | The 'opening' of a lens, a measure of its light gathering capability. Relative Aperture is a ratio between its focal length and effective aperture, measured in F numbers, generally the lower the better. |
| Auto Back Focus | The function to adjust flange back by moving the CCD position. This is useful for installation and upon colour to B/W switching. |
| Auto White Balance | Feature on colour cameras whereby the camera constantly monitors the light and adjusts its colour to maintain white areas. |
| Auto-terminating | Feature whereby the equipment automatically selects the correct termination depending on whether the video output BNC is connected. |
| Auto-tracking | A function which controls PTZ to chase a moving object with image recognition and image processing software. Advanced auto tracking for WV-CW970 series is a more accurate Auto tracking with template matching algorithm which processes shape, colour and contrast of the object. |
| B.L.C. (Back Light Compensation) | A feature of CCD cameras which electronically compensates for high background lighting to give detail which would normally be silhouetted. |
| 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. |
| Balun (Balanced Unbalanced) | A device that connects a balanced line, such as twisted pair, to an unbalanced line, such as coax cable. |
| Band Width | The frequency range that an electronic circuit can accept. |
| Bandwidth | The range of frequencies available for signalling the difference between the highest and lowest frequencies of a band, measured in Hertz |
| Base-Band Video | Unmodulated video signal suitable for display on a monitor but not a domestic TV. |
| Baseband | A full-channel bandwidth transmission where digital signals are placed onto a transmission line with no change in their modulation. |
| Baud | Unit of signalling speed. The speed in baud is the number of line changes (in frequency, amplitude, etc.) or events per second. At low speeds, each event represents only one bit condition, and baud rate equals bps. As speed increases, each event represents more than one bit and baud rate does not truly equal bps. |
| Baud rate | Data transmission speed. |
| Bit (Binary Digit) | The smallest unit of information in a binary system; a one or zero condition. |
| Black Level | The level on a video signal, just above the sync pulses, where black portions of the picture are represented. |
| 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. BNC: Video connector, the most commonly used in CCTV. |
| byte | The byte is a unit of digital information in computing and telecommunications. It is an ordered collection of bits, in which each bit denotes the binary value of 1 or 0. Historically, a byte was the number of bits (typically 6, 7, 8, or 9) used to encode a character of text in a computer and it is for this reason the basic addressable element in many computer architectures. The size of a byte is typically hardware dependent, but the modern de facto standard is 8 bits, as this is a convenient power of 2. Most of the numeric values used by many applications are representable in 8 bits and processor designers optimize for this common usage. Signal processing applications tend to operate on larger values and some digital signal processors have 16 or 40 bits as the smallest unit of addressable storage (on such processors a byte may be defined to contain this number of bits). |
| C Mount | Long established industrial standard for connecting cameras and lenses, widely used in the CCTV industry. |
| C.C.I.R. (Comite Consultatif International des Radiocommunications) | The European TV standard 625 lines 50 fields. |
| Cable screen/shield | A conductor which forms a sheath around one or more insulated conductors. This reduces the effect of interference onto the conductors. This shield is usually metallic foil or stranded wire wrapped around the conductors. |
| Camera | Image capture device |
| CCD (Charged Coupled Device) | A 'chip' that performs the same function as a camera tube. |
| CD-ROM (Compact Disc Read-Only Memory) | A compact disk format used to hold text, graphics and hi-fi stereo in excess of 650 MB of data, which is equivalent to about 250,000 pages of text or 20,000 medium-resolution pages. |
| Chrominance (C) | The part of the video signal corresponding to the colour information. |
| Coax | An abbreviation for Coaxial Cable which is any cable that has a conductor and shield sharing the same axis. |
| Coaxial Cable | Any cable that has a conductor and shield sharing the same axis. |
| Composite Sync | A signal comprising of both Line and Field sync pulses but without any video information. |
| Composite Video | The full video signal, including both video data and sync pulses. |
| Compression | A number of methods to reduce the size of digital information. See J-PEG, M-PEG and Wavelets. |
| Conditional Refresh | Technique used in slow and fast scan where only small screen changes are transmitted. Up to a certain percentage of the on-screen picture can be updated before a full picture is required. |
| CS Mount (Special C mount) | New standard for connecting cameras and lenses. It has a shorter penetration into the camera, needed for many modern CCD designs. |
| CS to C Mount Adaptor (C Ring) | 5mm spacer ring used to enable the use of C mount lenses on CS mount cameras. |
| D.D. (Direct Drive) | An Auto Iris lens requiring a D.C. reference from the camera rather than the traditional video reference. |
| Daisychain | To connect devices in a series, one after the other where the transmitted signals go to the first device, then to the second and so on. |
| Data cable | Cable used for transmitting low level signals between system units. |
| dB | Decibel, a logarithmic unit for comparing two voltages, each 6dB doubles the voltage. |
| DC | Direct Current |
| Default | An assumption made by the system when no specific choice is given by the programme or the user. |
| Depth of Field | The area of acceptable focus of an image. The wider you set the aperture of a lens the lower the depth of field becomes. |
| Digital | A signal that levels are represented by binary numbers. These can be kept in a store. |
| Distribution Amplifier | A device that accepts a video signal and sends it out over a number of independent outputs. |
| DOS | A disk operating system in which programmes are stored on disk. |
| Duplex | A multiplexer with two frame stores allowing it to show multi-screen pictures while performing time multiplex recording. |
| DVD (Digital Video Disk, Digital Versatile Disk) | A de facto standard agreed on by the computer, consumer electronics and entertainment industries for storing 4.7 or more GB of data on a single optical disc the size of a CD. |
| DVR | Abbreviation of Digital Video Recorder, a device that uses digital techniques to record CCTV pictures. The results can be of higher quality than VHS or SVHS. Events can be found faster and there is no loss of quality when copies are made. |
| Dwell Time | The length of time a switcher will hold a camera before moving on to the next in sequence. |
| E.I. (Electronic Iris) | Automatically varies a CCD camera's shutter to mimic Auto Iris control, allowing fixed or manual iris lenses to be used in a wider range of areas. |
| EIA (Electronic Industries Association) | A standards organisation in the US specialising in the electrical and functional characteristics of interface equipment. |
| Encoded | The result of transferring information in a coded form to a medium. |
| Ethernet | A local area network (LAN) developed by Xerox, Digital Equipment Corp. and Intel. Standardised as IEEE 802.3 and ISO 8802.3. Ethernet connects up to 1024 nodes at 10 Mbps over twistedpair, coax and fibre optic cable. When a station is ready to send, it transmits its data packets onto the network, which is common to all nodes. All stations "hear" the data. The station that matches the destination address in the packet responds while the others do nothing. Ethernet is a data-link protocol and functions at the Physical and Data-link Levels of the OSI model (Layers 1 and 2). |
| Ethernet Address | A unique 48-bit number maintained by the IEEE/ISO and assigned to each Ethernet network adaptor. |
| Event | Valid transactions reported by Access Control and Monitoring Systems. |
| 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. |
| EXview™ | The latest interline CCD sensor from SONY that has increased sensitivity across the visible spectrum and the near IR. |
| Fast Ethernet | Generally refers to 100BASE-T and 100BASE-FX but may also include 100VG. |
| Field | One half of a frame, consisting of either the odd or the even numbered lines, 50 fields are transmitted every second. |
| Field of View | The view achieved with a particular lens; varies with the focal length. |
| Firewall | A network node set up as a boundary to prevent unauthorised traffic from one segment to cross over to another. Firewalls are used to improve network traffic, as well as for security purposes. |
| Flash memory | A memory chip that holds its content without power but must be erased in fixed blocks rather than single bytes. Block sizes typically range from 512 bytes up to 256KB. |
| Focal Length | Of a lens, the distance in millimetres, between its secondary principal point and its focal point. The higher the number the greater the magnification and the less the field of view. |
| Focal Point | The point on the axis of a lens to which parallel rays of light will cover. |
| Format | How the computer arranges the information onto disk. Can also apply to printers. |
| Frame | One complete TV picture made up of approximately 625 lines. 25 frames are transmitted every second. |
| Frame Relay | Packet-switched network similar to X.25 but with end-to-end error-checking and high-speed transmission rates. |
| Frame Store | Digital information store capable of holding a complete frame of video information. |
| Frame Transfer CCD | Type of CCD chip which consists of vertical charge transfer channels placed side by side. During vertical blanking, the charge generated in the light sensitive imaging area is rapidly transferred into a shielded storage area. During the horizontal blanking, this charge is shifted down a line at a time into a horizontal shift register where it is clocked out during each line period to form the video signal. |
| Full Picture Update | The technology which enables a transmission system to update a high quality full picture on each picture refresh at very fast speeds. |
| Galvanometric (galvometric) | One method of converting the small electric currents produced by Auto Iris circuits into physical movement of the iris diaphragm. Used in both Auto Iris and Direct Drive lenses. |
| Gamma | A camera adjustment that ensures a linear correlation of light gain on the entire system eg. A doubling of light input gives double light output. |
| Gateway | A computerised device that performs protocol conversation between different types of networks or applications. |
| Gen. Lock (see ext. sync) | To synchronize one piece of equipment to the sync pulses of another. |
| Gigabit Ethernet | Technology that adapts the Ethernet model for data transmission at 1 Gbps or higher. |
| Ground Loop | An unwanted continuous or temporary ground current flowing back and forth between two devices that are at different ground potentials. |
| Hard Disk Drive | Non volatile digital data storage device used in computers. Come in various storage sizes, normally measured in giga-bytes. See Hard Disk Recorder. |
| Hardwired | Method of controlling camera points using multicore cable. |
| HDR | Abbreviation of Hard Disk Recorder, a device that uses digital techniques to record CCTV pictures to a hard disk. The results can be of higher quality than VHS or SVHS, events can be found faster and there is no loss of quality when copies are made. |
| Hot Swapping | Removing and replacing a component of a larger system while the system is receiving power and operating. |
| HTML (Hypertext Mark-up Language) | A standard for defining documents with hypertext links. HTML is a subset of SGML (Standard Generalised Mark-up Language) and is used to establish links between documents on the World Wide Web. |
| HTTP (Hypertext Transfer Protocol) | The clients/server protocol used for connections to servers on the World Wide Web. Addresses of Web sites begin with an http://prefix. |
| Hub | A central connecting device in a network that joins communications lines together in a star configuration. |
| Hz (Hertz) | Cycles per second |
| I.R. (Infra Red) | A range of frequencies lower than visible red light used for covert surveillance or as a low cost wireless video link. |
| Ident | Number or title super-imposed on a video signal. |
| Image Sensor Format | Size of the CCD element in the camera. |
| Impedance | The effective resistance of an electronic circuit to an A.C. signal. |
| Interlace (2:1 interlace) | The accurate combining of two fields, one odd one even, into a single frame. |
| Interleaving | Method used with alarms or activity detection which allows extra frames of video from alarmed cameras to be added to a time multiplexed sequence whilst a state of alarm exists. |
| Interline Transfer CCD | Type of CCD chip in which the photosensors acquire and store an electric charge according to the intensity of light falling on them. The charges are first transferred to a vertical shift register and then a horizontal shift register. This is controlled by an external pulse timing system. |
| Internal Sync (crystal controlled) | A camera that generates its sync pulses without reference to any other source. Normally using a crystal controlled oscillator. |
| Internet | Any large network made up of several smaller networks.A group of networks that are interconnected so that they appear to be one continuous large network and can be addressed seamlessly at the OSI Network layer through routers. The industry name for the Worldwide interconnected network. Based upon the original ARPANET network, it's used as a reference resource, a way of sending e-mail and an online chat room for users around the world. |
| Intranet | A network connecting a related set of standard Internet protocols and files in HTML format with employees using Internet browsers in an organisation's network and within the corporate firewalls. |
| IP (Internet Protocol) | The protocol used in gateways to connect networks at the OSI Network Layer (Layer 3) and above. IP routes a message across networks. |
| IPS | Number of images in a second for recording, display or transmission. This is used for digital video (non-interlaced video) instead of FPS (Frames per second) or fps (Fields per second) which is used for NTSC or PAL video signal because there is no such idea as “A frame consists of an odd and an even field” in digital video (non-interlaced video) in most cases. Even though it is “Image per second”, it can be called frame rate depending on the context. |
| Iris (Iris diaphragm) | Adjustable diaphragm that regulates the amount of light passing through a lens. |
| ISDN (Integrated Services Digital Network) | A digital switched network used to transmit voice, data, images or video. Also see BRI |
| J-PEG | Joint Picture Expert Group. A popular suite of digital compression tools. Originally for use with "still" pictures but often used in CCTV products. |
| Kb | Kilobyte, or one thousand bytes or characters of information. |
| Kilo | Order of magnitude; 10 3 |
| LAN | A Local Area Network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. The defining characteristics of LANs, in contrast to wide-area networks (WANs), include their usually higher data-transfer rates, smaller geographic area, and lack of a need for leased telecommunication lines. |
| LCD | Liquid Crystal Display. A type of flat screen display. |
| Lens Calculator Software | A computer program for specifying correct lenses. |
| Lens Calculator Wheel | Used for calculating a lens size or distance from a camera to the subject. |
| Line Amplifier (Video line corrector) | A device to make good the loss of signal strength and quality due to long cable runs. |
| Line Fed Camera | A camera that receives its power along the same cable that is used to send its picture back to the monitor. |
| Line Lock | To synchronize the field sync pulses, of an AC powered camera, to the frequency of the voltage input (line voltage). |
| Linux | A freeware, clone version of the UNIX‚ System V release 3.0 kernel that runs on PC x86 machines and other platforms. |
| Local Area Network (LAN) | A local area network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. The defining characteristics of LANs, in contrast to wide-area networks (WANs), include their usually higher data-transfer rates, smaller geographic area, and lack of a need for leased telecommunication lines. |
| Looping | Video input of a piece of video equipment both unterminated and including the relevant sockets for the extra coaxial cables. |
| LS | Level of Sensitivity. This is to set the sensitivity for comparing differences between consecutive images. The greater the differences, the more likely the motion will be detected. |
| Luminance (Y) | The part of a video signal that consists of the monochrome data. |
| Lux | Metric measure of the light striking a surface. The light available from that surface will depend on how reflective it is. |
| M-PEG | Moving Picture Expert Group. A suite of digital compression tools specifically designed to video images. |
| Macro | Feature allowing you to pre-programme frequent system configurations for selection by a single keystroke or optionally by alarm inputs. |
| Matrix Switcher | A switcher able to route any of its camera inputs to any of its monitor outputs; a name usually reserved for large systems, that often includes telemetry control. |
| Mb | Megabyte, or one million bytes or characters of information. |
| Mechanical Focus (Back-focus,racking) | 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. |
| Microwave | Radio frequencies between 1 - 30 GHz used for video transmission over medium/long distance. |
| Modem | Modulator/Demodulator.A device used to convert serial digital data from a transmitting terminal to an analogue signal (carrier) for transmission over a telephone channel or to reconvert the transmitted analogue signal to serial digital data for acceptance by a receiving terminal. |
| Noise | Video Signal interference that usually appears as graininess or snow on the picture. |
| Octet | The term octet was explicitly defined to denote a sequence of 8 bits because of the ambiguity associated with the term byte and is widely used in communications protocol specifications. |
| PAL | Phase Alternate Line Colour Video Signal standard for most of Europe, Australia and the Middle East - 625 Lines, 50Hz |
| Patch Panel | A panel that joins or terminates many different circuits |
| Photocell | A device used to detect changes in light level and provide an automatic switched output when lighting levels fall to a predetermined level |
| PIR | PIR is the abbreviation of “Passive Infra Red”, which is a motion sensor to detect heat from moving objects, such as human bodies and animals. When any motion is detected, P.I.R. will trigger the alarm system. The TV will show you what your cameras see. With P.I.R., you can always keep an eye on visitors at the front door, intruders in the garage, or any place within its detection coverage. With it, our products can detect moving objects within wider detection coverage to provide our customers optimum security and protection. |
| PSU | Power Supply Unit |
| PTZ | Pan Tilt and Zoom. A camera which can be controlled via Joystick or DVR and moved up/down, left/right and zoomed in/out. |
| QAM | Quadrature Amplitude Modulation. Method for modulating two carriers. The carriers can be analogue or digital. |
| QCIF | Quarter Common Intermediate Format. A videoconferencing format that specifies data rates of 30 frames per second (fps), with each frame containing 144 lines and 176 pixels per line. This is one fourth the resolution of Full CIF. QCIF support is required by the ITU H.261 videoconferencing standard. |
| Quad display | Equipment that simultaneously displays four images from four separate sources on a single monitor each occupying a quadrant of the screen. |
| RAID 1 | RAID 1 (Redundant Array of Independent Disks Level 1) writes identically data to two drives to protect against data loss from a single disk drive failure. |
| RAID 5 | RAID 5 (Redundant Array of Independent Disks Level 5) writes data to three or more hard disk drives to allow data to be recovered from a hard disk drive failure. |
| RAID 5 Board | An interface board that allows RAID5 to be utilised on a recorder. |
| Remote Access | The ability of a computer in one location to connect to a device at another location or site. |
| Roll | A loss of vertical synchronization which causes the picture to move up or down on a receiver or monitor. |
| router | A network hardware device that routes traffic between LANs and WANs |
| RS-232 | A commonly used computer serial interface. A data communication industry standard for the serial transmission of information. Distance without modems is limited. |
| RS-422 | EIA interface standard that generally operates in conjunction with RS-449 and specifies electrical characteristics for balanced circuits and extends transmission speeds and distances beyond RS-232/V.24. RS-422 is a balanced voltage system with a high level of noise immunity. |
| RS-485 | Balanced interface similar to RS-422/V.11 but using tri-state drivers for multidrop applications. |
| Rugby Clock | Radio signal to synchronize equipment clocks accurately and that automatically adjusts the BST setting. |
| S-VHS (Super VideoHome System) | Format on high resolution VHS video recorders, capable of giving greatly improved picture if all features are used. VHS compatible. |
| S.E.C.AM. (Systeme Electronique Couleur Avec Memoire. See CCIR) | Colour TV system used in France. |
| S/N Ratio (Signal to Noise Ratio) | Measure of noise levels of a video signal; the higher the number the better. |
| SCART | Standard European 20 pin connector used for carrying both video and audio signals in domestic TV appliances, now utilised on some CCTV equipment. |
| Single-Mode Fibre | An optical fibre that supports only one mode of light propagation above the cut off wavelength. The core diameters are usually between 5 and 10 micrometres (um). |
| SS | Spatial Sensitivity. This generally sets the amount of space required by an object to activate an event. |
| Tearing | A term used to describe a picture condition in which groups of horizontal lines are displaced in an irregular manner. |
| Telemetry | 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 | A lens where the focal length is longer than the physical length of the lens, not to be confused with a zoom lens. |
| Termination | 1. The connection of a discreet impedance at the end of a transmission line. When the characteristic impedance of the cable (75 Ohms in CCTV) is the value used (as should always be the case) the maximum power is transferred with no reflections. 2. It can refer to the physical act of terminating a cable with a special connector, which for coaxial cable is usually BNC. For optical fibre cable, the most common Termination in CCTV is the ST connector. |
| TFT | Thin-Film-Transistor. This technology is used mainly for manufacturing flat computer and video screens that are superior to the classic LCD screens. Colour quality, fast response time and resolution are excellent for video. |
| TS | Time Sensitiivty. The length of time required for an object to remain in the detection zone to trigger an event. |
| TVL | TeleVision Lines. The measure of resolution of either a camera output or a monitor display. It is limited by the frequency response of the system or the Chroma sub carrier. |
| Twisted-pair | A cable composed of two small insulated conductors twisted together. Since both wires have nearly equal exposure to any interference, common mode noise is high, but the differential noise is slight thus common mode noise is rejected in a twisted pair line. Twisted pair cable is used for balanced line transmission. |
| Unbalanced signal | In CCTV, this refers to a type of video signal transmission through a coaxial cable. It is called unbalanced because the signal travels through the centre core and returns via an earthed condutor. One conductor is a fixed voltage ie earth and only the other moves. In a balanced line system neither conductor is referenced to earth. |
| UPS | Uninterruptible Power Supply. These are power supplies used in the majority of high security systems, whose purpose is to back-up the system when the mains power fails. The duration of this depends on the size of the UPS, usually expressed in output VA (or kVA), and the hold up time expected from fully charged batteries. There are two common types, "off line" and "on line". Off line uses a switch to change from mains to battery operation, thus there can be a short break in the output. On Line UPSs are a type where the convertor is always working, hence there is no switch over break at the ouput. |
| UTP | Unshielded Twisted Pair. A cable medium with one or more pairs of twisted insulated copper conductors bound in a single sheath, with no overall or individual screen. Now the most common method of bringing telephone signals and data to the desktop. |
| Varifocal Lens | A cctv camera lens whose focal length / viewing angle can be manually adjusted to suit the camera view required. Typical Vari Focal lens lengths are: 2.5mm-10mm, 3.5mm-8mm, 5mm-50mm |
| VGA | Video Graphics Array |
| Video in-line amplifier | A device providing amplification of a video signal. |
| WAN | A wide area network (WAN) is a computer network that covers a broad area (i.e. any network whose communications links cross metropolitan, regional, or national boundaries). This is in contrast with personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs) which are usually limited to a room, building, campus or specific metropolitan area (e.g. a city) respectively. |
| Zoom Lens | A lens which has variable focal lengths. The image can be 'zoomed' in or out whilst the view of the camera remains in focus. |
| Zoom ratio | A mathematical expression of the two extremes of focal length available on a particular zoom lens |