CCTV Glossary
Index
A
Analog High Definition (AHD) -is an alternative standard for HD data transmission utilized by security industry chip manufacturers NextChip and Eyenix. AHD solutions are capable of transmitting 720p @ 25-30 fps while minimizing data loss. AHD recorders are compatible with all analog and like-branded AHD cameras, in limited configurations. AHD currently offers a lower max resolution vs. other HD CCTV formats - at 720p - but is reportedly launching 1080p models in late 2014. However, AHD delivers a lower quality image than both HD-SDI and HD-TVI technology. The technology is capable of long video transmission distances (inferior only to HD-TVI over twisted pair / CAT5), but is limited in both camera compatibility and configurability – and currently offers no IP camera support.
| AHD Facts | ||
|---|---|---|
| Max Resolution | 720p (1080p models reportedly launching in late 2014) | |
| Transmission Distance | Coaxial Cable (RG59) | 1600’ |
| Twisted Pair (CAT5) | 492’ | |
| DVR Input Compatibility | Analog | All cameras, on limited channels, in limited configurations |
| HD | Like-branded AHD cameras, on any channel, in any configuration | |
| IP | N/A | |
| Standard Protocol(s) | AHD 1.0 (TX and RX) | |
AC Adapter - Also called a power supply. All CCTV devices need power of some sort. Each device has its own power requirements (usually 12 volts with minimum amperage). The power coming out of the wall (in the UK) is 240 DC. The adaptor converts the AC power to DC power and will adjust it to specified amperage.
AGC - Automatic Gain Control. A circuit for automatically controlling amplifier gain in order to maintain a constant output voltage with a varying input voltage within a predetermined range of input-to-output variation.
Alarm input - An input connection to a security VCR or DVR that triggers the unit to start recording if the alarm is triggered.
Analog - The opposite of digital is analog. A typical analog device is a clock in which the hands move continuously around the face. Such a clock is capable of indicating every possible time of day. In contrast, a digital clock is capable of representing only a finite number of times (every tenth of a second, for example). In general, humans experience the world analogically. Vision, for example, is an analog experience because we perceive infinitely smooth gradations of shapes and colors. Most analog events, however, can be simulated digitally. Photographs in newspapers, for instance, consist of an array of dots that are either black or white. From afar, the viewer does not see the dots (the digital form), but only lines and shading, which appear to be continuous. Although digital representations are approximations of analog events, they are useful because they are relatively easy to store and manipulate electronically.
Angle of view - For security cameras, this refers to the angular range in degrees that you can focus the camera on without distorting the image. When focusing close up, you can generally see a wide angle of view. If the focus is distant, the angle of view is smaller or narrower.
Aperture - In television optics, it is the effective diameter of the lens that controls the amount of light reaching the photoconductive or photo emitting image pickup sensor.
Asymmetrical Digital Subscriber - A method for moving data over regular phone lines. An ADSL circuit is much faster than a regular phone connection, and the wires used are the same wires used for regular phone service. ADSL supports data rates from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate). ADSL requires a special ADSL modem.
Audio/Video Interleave (AVI) - An AVI file is a sound and motion picture file that conforms to the Microsoft Windows Resource Interchange File Format (RIFF) specification. AVI files (which end with an .avi extension) require a special player that may be included with your web browser.
Auto Balance - A system for detecting errors in color balance in white and black areas of the picture and automatically adjust the white and black levels of both the red and blue signals as needed for correction.
Auto Iris - A lens in which the aperture automatically opens or closes to maintain proper light levels on the faceplate of the camera pickup device.
Automatic Brightness Control (ABC) - In display devices, the self-acting mechanism which controls brightness of the device as a function of ambient light.
Automatic Gain Control (AGC) - A process by which gain is automatically adjusted as a function of input or other specified parameter.
Automatic Iris Lens - A lens that automatically adjusts the amount of light reaching the imager.
Automatic Light Control (ALC) - The process by which the illumination incident upon the face of a pickup device is automatically adjusted as a function of scene brightness.
Automatic White Balance (AWB) - A feature on color cameras that constantly monitors the light and adjusts its color to maintain white areas.
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B
Back Light Compensation (BLC) - This button compensates the exposure for scenes in which there is a strong light behind the subject. Generally, this situation results in your main subject being underexposed, but the backlight button causes your camera's iris to open up, thus slightly overexposing the rest of the scene, while properly exposing your main subject. If you can manually adjust the exposure compensation, try making small adjustments until you see the desired results.
Balun - A Video Balun enables the transmission of video using unshielded twisted pair wire instead of coaxial cable. The word "balun" comes from combining the terms balanced and unbalanced. The function of a balun is to transform an unbalanced signal into a balanced signal. When video signal is transmitted through coaxial cable, the distance traveled by the signal is limited because the signal is in the form of an unbalanced signal that is susceptible to Radio Frequency Interference or noise. Coax cable incorporates special shielding to minimize noise. Video Baluns transform the video signal into a balanced form in which each wire in the twisted pair transmits an identical signal with opposite polarized magnetic fields. Noise affects each signal equally. When the signals are combined, the noise is cancelled out. By using a designed balun, an unshielded twisted pair wire can transmit video for much longer distances than coax cable and with a lower cable cost.
Bandwidth - The bandwidth determines the rate at which video can be sent through a network; the greater the bandwidth, the more video that can be sent in a given amount of time; usually measured in bits-per-second.
Baud - The baud rate is how many bits can be sent or received per second.
Bitmap - A bitmap is digital graphic that basically consists of a map of dots. Bitmaps include GIF, JPEG and other file formats.
BNC connector - Short for Bayonet Neill Concelman connector (sometimes erroneously called a British Naval Connector or Bayonet Nut Connector). A type of connector used with coaxial cables such as the RG-58 A/U cable used with the 10Base-2 Ethernet system. The basic BNC connector is a male type mounted at each end of a cable. This connector has a center pin connected to the center cable conductor and a metal tube connected to the outer cable shield. A rotating ring outside the tube locks the cable to any female connector.
Brightness - The attribute of visual perception in accordance with which an area appears to emit more or less light. Luminance is the recommended name for the photo-electric quantity which has also been called brightness.
Broadband - A general term for different types of high-speed, high-bandwidth connections to the Internet, including ADSL and cable
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C
Category (CAT) 5 Cable - Cable that is capable of transmitting data at high speeds (100 megabits per second and faster). CAT 5 cable is commonly used for voice and data applications. Usually comes with RJ45 connectors.
CCTV - Closed circuit television. Television system intended for only a limited number of viewers, as opposed to broadcast TV. With the arrival of IP-based surveillance, analog CCTV systems are now being superseded by improved digital technology.
Charge Coupled Device (CCD) - An electronic memory that is charged by light. It is commonly used in still cameras, camcorders and scanners to capture light for conversion to electricity. CCDs are analog devices that hold a variable charge and are thus capable of recording the varying shades of light. To convert the content of CCDs into the digital realm, analog to digital (ADC) converters quantify the variable charge into a discrete number of colors.
Charge-Coupled Device (CCD) - CCTV cameras that are CCD will give sharper, better defined pictures. All professional level cameras will be CCD.
CMOS - Complementary Metal Oxide Semiconductor. Similar to a CCD, it also detects light for conversion into a signal. Lesser image clarity than CCD, but more compact in size with lower power usage.
C Mount Lens & CS Mount Lens - There are two main types of lenses used in security cameras. The C mount lens has a flange back distance of 17.5mm. The CS mount lens has a flange back distance of 12.5mm. C mount lenses therefore have a longer focal distance. CS mount became widely used, because it its more practical for many of today's more compact cameras. Lenses are often supplied with a 5mm spacer ring (sometimes called a C ring) that allows a C mount lens to be used on a CS camera. Most modern security cameras are CS.
Coaxial Cable - A particular type of cable capable of passing a wide range of frequencies with very low signal loss. Such a cable in its simplest form consists of a hollow metallic shield with a single wire accurately placed along the center of the shield and isolated from the shield.
Codec - Short for compressor/decompressor. A codec is any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both. Examples of Codecs include Wavelet, MPEG-4, and JPEG.
Composite Video - A video color format that combines all three YUV video signals into one channel. The first video signal to include color, composite video transmits brightness/luma (Y) and colors/chroma (U and V) over one cable. NTSC, PAL and SECAM television are composite video.
Compression Technology - This is the Codecs used for compressing and decompressing video data.
Contrast - The range of light to dark values in a picture or the ratio between the maximum and minimum brightness values.
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D
Day/Night Cameras - Day/Night Cameras are regular cameras with an especially sensitive CCD chip that allows a good image to be captured in very low ambient lighting (regular lighting not infrared).
Definition - The fidelity of a television system to the original scene.
Depth of Field - The in-focus range of a lens or optical system. It is measured from the distance behind an object to the distance in front of the object when the viewing lens shows the object to be in focus.
Depth of Focus - The range of sensor-to-lens distance for which the image formed by the lens is clearly focused.
Digital - Describes any system based on discontinuous data or events. Computers are digital machines because at their most basic level they can distinguish between just two values, 0 and 1, or off and on. There is no simple way to represent all the values in between, such as 0.25. All data that a computer processes must be encoded digitally, as a series of zeroes and ones.
Distortion - The deviation of the received signal waveform from that of the original transmitted waveform.
Distribution Amplifier - A device that provides several isolated outputs from one looping or bridging input, and has a sufficiently high input impedance and input-to-output isolation to prevent loading of the input source.
Downstream - The downloading of data from the Internet to the PC. ADSL has both upstream and downstream data rates.
Duplex - A circuit that permits transmission in both directions. In CCTV, duplex is often used to describe the type of multiplexer that can perform two functions simultaneously: recording in multiplex mode and playback in multiplex mode.
DVR (Digital Video Recorder) - A digital video recorder is basically a computer that converts the incoming (analog) signal from the cameras to digital, and compresses it, and stores it. The DVR replaces the function of a multiplexer (or quad or switcher) and a security VCR. There are many advantages of digital video recorders over their analog counterparts.
Dynamic IP address - The term used to describe how an IP address is dynamically assigned to computers as and when needed. Unlike Static IP addresses, the IP address is temporary e.g. when you connect to your ISP using a dial-up connection , your PC or router will be dynamically assigned an IP address while you are on-line. This form of IP addressing is commonly used for consumer ADSL service.
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E
Ethernet - Ethernet is a standard technology for network communications in LANs (Local Area Networks). Ethernet LANs use twisted pair cabling, with network devices connecting to a central cable or hub. The most common Ethernet systems are 10BASE-T and 100BASE-T10, which transmit data at speeds of 10 Mbps and 100 Mbps.
EDID(Extended display identification data) - is a data structure provided by a digital display to describe its capabilities to a video source (e.g. graphics card or set-top box). It is what enables a modern personal computer to know what kinds of monitors are connected to it.
F
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F Stop - Photographers set their exposure using a combination of shutter speeds and f/stops to get the correct amount of light on the film. The shutter speed regulates how long the film is exposed to light coming through the lens. The f/stop regulates how much light is allowed through the lens by varying the area of the hole the light comes through. For any given film speed and lighting combination there is one correct amount of light to properly expose the film. This amount of light can be achieved with many different combinations of f/stops and shutter speeds. This section goes over the f/stop and especially its initially confusing numbering at some length. F/stops is a bit more confusing because the numbers appear so arbitrary. This is the standard sequence of f/stops from f/1.4 to f/22. Although it doesn't seem intuitive at first, in this sequence the f/1.4 setting lets in the most light while the f/22 setting lets in the least. Also, each of these f/stops has precisely the same halving/doubling relationship as the shutter speed sequence. 1.4 2.0 2.8 4 5.6 8 11 16 22 On the face of it, going from f/4 to f/5.6 doesn't sound like halving the amount of light. What's more, 5.6 is a larger number and sounds like it ought to be more light, not less. Neither does f/4 to f/2.8 sound like doubling the amount of light. In fact, each of the numbers in this sequence is a halving/doubling of the amount of light from its immediate neighbors, just like the shutter speed settings are.
Field - One of the two equal but vertically separated parts into which a television frame is divided in an interlaced system of scanning. A period of 1/60 second separates each field start time.
Field of View - The maximum angle of view that can be seen through a lens or optical instrument.
Firewall - A firewall is a set of related programs, located at a network gateway server that protects the resources of a private network from users of other networks.
Focal Length - Of a lens, the distance from the focal point to the principal point of the lens.
| Focal Length |
Imaging Device Size |
||
| 1/4" | 1/3" | 1/2" | |
| 2.8 mm | 64˚ | 80˚ | 97˚ |
| 4.0 mm | 45˚ | 60˚ | 74˚ |
| 6.0 mm | 30˚ | 38˚ | 57˚ |
| 8.0 mm | 23˚ | 30˚ | 40˚ |
| 12.0 mm | 15˚ | 20˚ | 30˚ |
| 16.0 mm | 11˚ | 15˚ | 22˚ |
| 50.0 mm | 4˚ | 5˚ | 7˚ |
Focal Plane - A plane (through the focal point) at right angles to the principal point of the lens.
Focal Point - The point at which a lens or mirror will focus parallel incident radiation.
Frames and Resolution - Administered by the FCC. NTSC broadcasts 60 half frames per second, which is known as 60 "fields" per second in TV jargon (59.94 fields per second to be exact). NTSC uses 525 lines of resolution. The first 480 lines in each frame are the image, and the last 45 are the "vertical blanking interval" (VBI), which was designed to give the electron gun time to reposition itself from the bottom of the last frame to the top of the next.
Frames per Second (fps) - This refers to the number of pictures that can be recorded or displayed per second. A television displays 25fps and is referred to as real time. This should not be confused with fields per second. Two fields per second is equivalent to one frame per second. Recommended frame rates are as follows: POS Monitoring = 25fps-Retail Surveillance = 16fps-Door/Car Monitoring = 4fps
FTP (File Transfer Protocol) - is a network protocol used to transfer files from one computer to another, or between devices on the network. An FTP client can connect to an FTP server to access and manipulate the files stored on that server.
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G
Gain - An increase in voltage or power, usually expressed in dB.
Ghost - A spurious image resulting from an echo.
Gigabyte (GB) - This unit is typically used to measure large data storage or data transfer capacities (by current standards). 1GB = 1024 MB = 1,048,576 KB = 1,073,741,824 bytes.
Gray Scale - Variations in value from white, through shades of gray, to black on a television screen. The gradations approximate the tonal values of the original image picked up by the TV camera.
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H
High-Definition Composite Video Interface (HD-CVI) - is a proprietary HD Analog technology developed by the Chinese security product manufacturer, Dahua. HD-CVI solutions are capable of transmitting HD video over standard analog coaxial cabling up to 1300' (1080p) and 1600' (720p). HD-CVI recorders are compatible with all analog and like-branded HD-CVI cameras, in limited configurations. HD-CVI offers comparable resolution to other HD CCTV formats, but a lower quality image than both HD-SDI and HD-TVI technology. The technology is capable of long video transmission distances (second only to HD-TVI), but is limited in both camera compatibility and configurability.
| HD-CVI Facts | ||
|---|---|---|
| Max Resolution | 1080p | |
| Transmission Distance | Coaxial Cable (RG59) | 1300’ (720p), 1600’ (1080p) |
| Twisted Pair (CAT5) | 650’ | |
| DVR Input Compatibility | Analog | All cameras, on limited channels, in limited configurations |
| HD | Like-branded HD-CVI cameras, on any channel, in any configuration | |
| IP | N/A | |
| Standard Protocol(s) | HDCVI 2.0 | |
High-Definition Transport Video (HD-TVI) - is the HD Analog technology introduced. HD-TVI solutions are capable of transmitting zero latency 720p or 1080p HD video over standard coaxial cabling up to 1600'. HD-TVI "tribrid" recorders are compatible with all analog, all HD-TVI cameras, and supported IP cameras, on any channel and in any configuration. HD-TVI offers comparable resolution to other HD CCTV formats, a high quality image, is capable of longer transmissions, and is the most flexible option for camera compatibility, hybrid capabilities, and overall configurability.
| HD-TVI Facts | ||
|---|---|---|
| Max Resolution | 1080p | |
| Transmission Distance | Coaxial Cable (RG59) | 1600’ |
| Twisted Pair (CAT5) | 700’ | |
| DVR Input Compatibility | Analog | All cameras, on any channel, in any configuration |
| HD | Any HD-TVI camera, on any channel, in any configuration | |
| IP | Supported IP cameras, on 2 channels, in any configuration | |
| Standard Protocol(s) | N/A, Open Source | |
High-definition Serial Digital Interface (HD-SDI) - was the first HD Analog format introduced to the video security market. HD-SDI solutions are capable of transmitting 720p or 1080p resolution video over standard coaxial cable. HD-SDI recorders are compatible with like-branded HD-SDI cameras and limited analog models, in limited configurations. HD-SDI offers comparable resolution to other HD CCTV formats, and arguably produces the highest quality image. However, the technology is only capable of shorter video transmission distances, and is limited in both camera compatibility and configurability. Additionally, a slower adaption rate of the technology has resulted in significantly higher prices for HD-SDI products. - A GSM transmission standard that allows data to be transferred at up to 28.8kbps.
| HD-SDI Capabilities | ||
|---|---|---|
| Max Resolution | 1080p | |
| Transmission Distance | Coaxial Cable (RG59) | 492’ |
| Twisted Pair (CAT5) | 350’ | |
| DVR Input Compatibility | Analog | Limited models, on limited channels, in limited configurations |
| HD | Like-branded HD-SDI cameras, on any channel, in any configuration | |
| IP | N/A | |
| Standard Protocol(s) | SMPTE 292M | |
Hard Disk Drive (HDD) - The storage device usually fixed inside of your computer or DVR used to store information.
H.264 - also known as MPEG-4 AVC (Advanced Video Coding), is a video compression standard that offers significantly greater compression than its predecessors. The standard offers up to twice the compression of MPEG-4 ASP (Advanced Simple Profile). In addition to improvements in perceptual quality, the H.264 standard can provide DVD-quality video such at under 1 Mbps.
H.265 - it's full name is High Efficiency Video Coding (HEVC). this new video codec will compress video files to half the size possible using the most-efficient current encoding format, MPEG-4, aka H.264 (used on Blu-ray discs and some satellite TV broadcasts).
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I
Image Compression - Image compression reduces the file size of video images to optimize bandwidth while streaming surveillance footage. The most common compression technologies for IP network cameras are Motion JPEG and MPEG-4. H.264 is the latest compression technology that significantly reduces the file size of high-quality video images.
Image Sensor - A image sensor is a light-sensitive image device available in many IP network cameras. The sensor transforms light into electronic signals. Image sensors provide strong light sensitivity allowing for video surveillance in low-light conditions.
Image Intensifier - A device coupled by fiber optics to a TV image pickup sensor to increase sensitivity. Can be single or multi stage.
Incident Light - The light that falls directly on an object.
Information Technology (IT) - Processing information by computer. IT is the latest moniker for the industry. There have been several before it, namely "electronic data processing" (EDP), "management information systems" (MIS) and "information systems" (IS). The term became popular in the 1990s.
Interference - Extraneous energy which tends to interfere with the reception of the desired signals.
Internal Sync - Devices with internal sync have an internal crystal to provide sync pulses without needing reference from any external device.
IP (Internet Protocol) - IP (Internet Protocol) is a connectionless protocol used for transmitting data over a network. Data is divided into independent packets containing the IP address of both the sender and the recipient. Each computer or network device has its own unique IP address. The TCP/IP standard protocol that defines the IP datagram as the unit of information passed across an Internet and provides the basis for connectionless packet delivery service.
IP Address - An IP address is the unique address of a computer or network device connected to that network. IP addresses allow those network computers and devices to locate each other and transfer data back and forth. An IP address is written as a set of four numbers separated by periods (each number can range from 0 to 255). An example of an IP address is 123.123.4.5
IP Camera - An IP camera (or network camera) captures and transmits live video images directly over an IP network. Each camera has a built-in web server and its own IP address. IP cameras allow for remote viewing, recording, and management from anywhere using a web server or video management software.
Infrared (IR) - Low frequency light below the visible spectrum. Infrared is used in surveillance cameras to provide a light source to record images in dark and zero light conditions.
Infra Red Camera - Infrared cameras (night vision cameras) have special infrared lights installed around the perimeter of the camera lens. This provides special light that the camera uses to capture a good picture even in total darkness.
Iris - The iris (or aperture) is an opening in the camcorder's lens controlling how much light passes through to its CCDs. A larger iris setting allows more light to pass through your lens, while a smaller one allows less. The iris also affects your depth of field.
IP (Ingress Protection) Rating - It's an international standard (EN 60529) which classifies the degrees of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in electrical enclosures. The most common IP ratings in our industry are 65, 66, 67 and 68. So for quick reference, these are defined below:
- IP65 Enclosure - IP rated as "dust tight" and protected against water projected from a nozzle.
- IP66 Enclosure - IP rated as "dust tight" and protected against heavy seas or powerful jets of water.
- IP 67 Enclosures - IP rated as "dust tight" and protected against immersion.
- IP 68 Enclosures - IP rated as "dust tight" and protected against complete, continuous submersion in water.
IK (Impact Protection) Rating - used to measure Vandal Resistance Rating of camera enclosure. Degrees of protection provided by enclosures for electrical equipment against external mechanical impacts in accordance with IEC 62262. Rating numbers from IK01 (not protected) to IK10 (Protected against 20 joules impact. Equivalent to impact of 5kg mass dropped from 400 mm above impacted surface.)
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J
JPEG - Stands for Joint Photographic Experts Group who designed the standard. The amount of compression can be controlled to allow for a tradeoff between image quality and file size. JPEG is the most commonly used format for storing and sending images over the internet. This is a standard way of compressing images which works particularly well for photographic images (as opposed to graphic art).
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L
LCD (Liquid Crystal Display) - Liquid crystal displays (LCDs) offer several advantages over traditional cathode-ray tube displays that make them ideal for several applications. LCD’s are flat, and they use only a fraction of the power required by CRTs. They are easier to read and more pleasant to work with for long periods of time than most ordinary video monitors. There are several tradeoffs as well, such as limited view angle, brightness, and contrast, not to mention high manufacturing cost.
LED (Light Emitting Device) - is a type of light source which generates an infrared frequency when stimulated by electricity.
Lens - A transparent optical component consisting of one or more pieces of optical glass with surfaces so curved (usually Spherical), that they serve to converge or diverge the transmitted rays of an object, thus forming a real or virtual image of that object.
Lens Preset Positioning - Follower Pots are installed on lens that allows feedback to the controller information relevant to zoom and focus positioning allowing the controller to quickly adjust to a pre-selected scene and arrive in focus at the proper focal length automatically.
Lens Speed - Refers to the ability of a lens to transmit light, represented as the ratio of the focal length to the diameter of the lens. A fast lens would be rated f/8. The larger the f number, the slower the lens.
Light - Electromagnetic radiation detectable by the eye, ranging in wavelength from about 400 to 750 nm.
Line Amplifier - An amplifier for audio or video signals that feeds a transmission line. Also called program amplifier.
Local Area Network (LAN) - A communications system that links computers into a network, usually via a wiring based cabling scheme. LANs connect PCs, workstations and servers together to allow users to communicate and share resources like hard disk storage and printers. Devices linked by a LAN may be on the same floor or within a building or campus. It is user-owned and does not run over leased lines, though a LAN may have gateways to the PSTN or other private networks.
Loop Through - Also called looping. The method of feeding a series of high impedance circuits (such as multiple monitor/displays in parallel) from a pulse or video source with a coax transmission line in such a manner that the line is bridged (with minimum length stubs) and that the last unit properly terminates the line in its characteristic impedance. This minimizes discontinuities or reflections on the transmission line.
Loss - A reduction in signal level or strength, usually expressed in dB. Power dissipation serving no useful purpose.
Luminance - Luminous intensity (photometric brightness) of any surface in a given direction per unit of projected area of the surface, as viewed from that direction. Measured in footlamberts (fl).
Lux - International System (IS) unit of illumination in which the meter is the unit of length. One lux equals one lumen per square meter. A camera’s light gathering ability. The lower the number, the better the image in low light conditions. A sunny day would be about 100,000 lux; a full moon at night would be about 0.1 lux; street lighting would be about 1 to 10 lux; home/office lighting would be about 100 to 1000 lux. In relation to network cameras, lux is the measure of low-light sensitivity provided by the camera.
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M
Megabits Per Second (MBPS) - A measurement of the transmission speed of data measured in 1,048,576 bits per second.
Megapixel IP cameras - provide exceptionally high image detail and are the ideal choice for video surveillance applications where clear identification of people and objects is critical. A megapixel camera will also provide a broader field of view than a conventional surveillance camera, and allows users to zoom in on specific portions of a scene without a significant loss in image detail.
Milliampere(mA) - A unit of current equal to one thousandth of an ampere.
Modem-Modulate/Demodulate - Device for the transmission of data via dial-up networking.
Modulation - the process or results of the process, whereby some characteristic of one signal is varied in accordance with another signal. The modulated signal is called the carrier. The carrier may be modulated in three fundamental ways: by varying the amplitude, called amplitude modulation; by varying the frequency, called frequency modulation; by varying the phase, called phase modulation.
Monitor - A unit of equipment that displays on the face of a picture tube the images detected and transmitted by a television camera.
Motion Detection - In terms of IP-based surveillance, motion detection is a network camera application that allows users to trigger events such as recording, high-quality video streaming, and automated alerts to occur only when motion is perceived. Motion detection helps to optimize bandwidth and preserve storage space.
Motion Joint Photographic Expert (MJPEG) - This compression standard generally refers to JPEG images shown at high frame rate, generally 25 frames per second. It gives high quality video images, but the comparatively large file sizes of each individual image does put demands on the transmission bandwidth.
Motion Picture Experts Group (MPEG) - MPEG is an international standard for video compression. MPEG-1 is a low-resolution format currently used on the World Wide Web for short animated files. MPEG-2 is a much higher resolution format being developed for digital television and movies. MPEG-4 is increasingly being used in CCTV solutions.
MPEG4 - is a video and audio compression technology found in many IP network camera models. The MPEG4 compression standard aims to deliver superior image quality while optimizing bandwidth.
Multiplexer - A device primarily developed as a means to record multiple cameras simultaneously to a single video tape. They also allow viewing of multiple cameras on a single monitor in various arrangements.
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N
Network Camera - A network camera (or IP camera) captures and streams live video images directly over an IP network. Each camera has its own IP address and features a built-in web server. Network cameras allow for remote viewing, recording, and video management from anywhere using a web server or video management software.
Network Video Recorder (NVR) - A Network Video Recorder (NVR) is a hardware box that receives video streams over a LAN or WAN and captures them onto hard disk in digital format. Recording and playback can be managed remotely using a network PC.
Night Vision - Cameras that have night vision have the ability to see in low light conditions. To judge how dark it can be for your camera to work, look at the Lux rating on the camera. The lower the lux, the better it will see at night.
Noise - The word ‘noise’ originated in audio practice and refers to random spurts of electrical energy or interference. In some cases, it will produce a ‘salt-and-pepper’ pattern over the televised picture. Heavy noise is sometimes referred to as ‘snow’.
Non-Composite Video - A video signal containing all information except sync.
NTSC - (National TV Standards Committee) The committee that developed the television standards for the U.S, which are also used in Canada, Japan, South Korea and several Central and South American countries. Both the committee and the standard are called "NTSC."
NPT (National Pipe Thread) Taper - is a U.S. standard for tapered threads used on threaded pipes and fittings. In contrast to straight threads that are found on a bolt, a taper thread will pull tight and therefore make a fluid-tight seal.
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P
PAL (Phase Alternating Line) - A color TV standard that was developed in Germany. It broadcasts 25 interlaced frames per second (50 half frames per second) at 625 lines of resolution. Brazil uses PAL M, which broadcasts 30 fps. PAL is used throughout Europe and China as well as in various African, South American and Middle Eastern countries. PAL's color signals are maintained automatically, and the TV set does not have a user-adjustable hue control.
Pan and Tilt - A device upon which a camera can be mounted that allows movement in both the azimuth (pan) and in the vertical plane (tilt). IP cameras with panning capabilities can move back and forth horizontally in order to monitor wider areas. In many cases a camera's panning and tilting functionality can be controlled remotely from a network PC using video management software.
Pan/Tilt Preset Positioning - Follower pots are installed on pan/tilt unit to allow feedback to the controller and provides information relevant to horizontal and vertical positioning, allowing the controller to quickly adjust to a pre-selected scene automatically.
PCI Video Card - A PC card that allows video from analog cameras to be fed into a computer.
Picture Element - See Pixel
PIR - Passive Infrared. Widely used in devices to detect motion. A special lens on the front of the PIR divides the sensor into zones. An individual’s body heat radiation is detected as it moves through the sensor zones in front of the PIR.
Pixel - Short for Picture Element. A pixel is the smallest area of a television picture capable of being delineated by an electrical signal passed through the system of part thereof. The number of picture elements (pixels) in a complete picture, and their geometric characteristics of vertical height and horizontal width, provides information on the total amount of detail which the raster can display and on the sharpness of the detail, respectively. Monitor resolution is measured in pixels. CCTV pictures of 640 x 480 pixels (full screen) and 320 x 240 (quad screen) are most common.
Power over Ethernet (PoE) - With Power over Ethernet, a network device, such as an IP camera, receives power and transmits video and data over a single Ethernet cable. This allows for flexible installation in locations where power outlets aren't readily available. This is 2003 802.3af IEEE standard, PoE provides up to 15.4W of DC power to each device. Only 12.95W is assured to be available at the powered device as some power is dissipated in the cable.
PoE Plus, High Power PoE (PoE+) - The updated IEEE 802.3at-2009 PoE standard also known as PoE+ or PoE plus, provides up to 25.5 W of power. The 2009 standard prohibits a powered device from using all four pairs for power. Some vendors have announced products that claim to be compatible with the 802.3 at standard and offer up to 51 W of power over a single cable by utilizing all four pairs in the Category 5 cable.
Port Re-direction (Port forwarding) - This refers to pointing a port of a modem/router to an IP address where a PC or networked DVR can be found for viewing cameras over the internet.
Protocols - When data is being transmitted between two or more devices something needs to govern the controls that keep this data intact. A protocol is a formal description of message formats and the rules two computers must follow to exchange those messages.
Proxy Server - A server that acts as an intermediary between a user's computer and the computer they want to access. If a user makes a request for a resource from computer "A," this request is directed to the proxy server, which makes the request, gets the response from computer "A," and then forwards the response to the client. Proxy servers are useful for accessing World Wide Web resources from inside a firewall.
PSTN - Public Switched Telephone Network analog communications network used for day to day telephony and data transmission.
PTZ (Pan, Tilt, Zoom) - PTZ functionality is a feature available in many camera models. PTZ allows users to monitor large areas with a single network camera. Pan, tilt, and zoom functions can be controlled remotely so operators can follow activity and focus in on specific details.
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Q
Quad Processor - is a device which uses digital video to display pictures from 4 cameras on a single monitor.
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R
RCA Connector - A plug and socket for a two-wire (signal and ground) coaxial cable that is widely used to connect analog audio and video components. Also called a "phono connector". Rows of RCA sockets are found on the backs of stereo amplifiers and numerous A/V products. The prong is 1/8" thick by 5/16" long.
Real time video - is a picture with more than 24 frames per second, and therefore looks continuous.
Resolution - is a measure of picture definition and clarity and is represented by the number of lines. The greater the number of lines, the higher the resolution.
Resolution (horizontal) - The amount of resolvable detail in the horizontal direction in a picture. It is usually expressed as the number of distinct vertical lines, alternately black and white, which can be seen in a distance equal to picture height.
Resolution (vertical) - The amount of resolvable detail in the vertical direction in a picture. It is usually expressed as the number of distinct horizontal lines, alternately black and white, which can theoretically be seen in a picture.
Resolution, Limiting - The details that can be distinguished on the television screen. Vertical resolution refers to the number of horizontal black and white lines that can be resolved in the picture height. Horizontal resolution refers to the black and white lines resolved in a dimension equal to the vertical height and may be limited by the video amplifier bandwidth.
Retained Image - Also called image burn. A change produced in or on the target which remains for a large number of frames after the removal of a previously stationary light image and which yields a spurious electrical signal corresponding to that light image.
RF (Radio Frequency) - A frequency at which coherent electromagnetic radiation of energy is useful for communication purposes. Also, the entire range of such frequencies.
RG-59 - is a type of coaxial cable used for transmission of video signals up to 230m. It is the most popular cable used in CCTV.
RJ11 - A type of telephone connector. Standard in the US.
RJ45 - A standard network connector often found at the end of CAT-5 cable.
Roll - A loss of vertical synchronization which causes the picture to move up or down on a receiver or monitor.
Router - The role of a router can be described as a bridge between two or more networks. The function of the router is to look at the destination addresses of the packets passing through it, and thereafter decide which route to send these packets on.
RS232 - A standard for serial transmission of data between two devices. This defines the pin and plug in terms of size, shape and number of pins.
RS485 - also referred to as EIA-485 is a communications standard for serial communication between devices. When talking about surveillance systems, RS-485 is typically used as the protocal to allow computers and remote controllers to control the activity of cameras such as pan, tilt, rotate, and zoom operations. RS485 is an updated version of the original serial protocol, RS-232.
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S
Saturation - In color, the degree to which a color is diluted with white light or is pure. The vividness of a color, described by such terms as bright, deep, pastel, pale, etc. Saturation is directly related to the amplitude of the chrominance signal.
Scanning - The process of moving the electron beam of a pickup tube or a picture tube across the target or screen area of a tube. Sensitivity
Server - In general, a server is a computer program, or a computer running a server program, that provides services to other computer programs. A server appliance is a network-connected hardware appliance that provides dedicated applications to a network, while a web server is a computer program that delivers requested html files and pages to the client.
Serial Port - Also known as a communications port or COM port. The serial port is a location for sending and receiving serial data transmissions. These ports are known by the names COM1, COM2, COM3, and COM4.
Shutter - Ability to control the integration (of light) time to the sensor to less than 1/60 second; e.g. stop motion of moving traffic.
Shutter Speed - You may be familiar with still cameras which have mechanical shutters to allow light passing through the lens to reach the film or image sensor. There is usually no physical shutter on a DV camera, so it simulates one electronically; regulating the amount of time CCD collects light for a single field or frame of video before converting it into an image.
Signal-to-Noise Ratio (S/N Ratio) - This is the ratio between the signal strength and the noise levels on an audio or video signal.
Snow - Heavy random video noise.
Spike - A transient of short duration, comprising part of a pulse, during which the amplitude considerably exceeds the average amplitude of the pulse.
Static IP address - An IP address which is the same every time you log on to the Internet. The alternative to a dynamic IP address. Often standard for business broadband but not for domestic broadband.
Subnet - A division of a network into an interconnected, but independent, segment, or domain, in order to improve performance and security. Because traffic is often the heaviest within a department, and Ethernet is the common network technology, the subnet limits the number of nodes (clients, servers) that have to compete for available bandwidth to a confined geographic area.
Subnet Mask - A numeric designation, with the same format as an IP address, which determines how much of an IP address is used to partition a network using TCP/IP into smaller entities called subnets.
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T
Test Pattern - A chart especially prepared for checking overall performance of a television system. It contains various combinations of lines and geometric shapes. The camera is focused on the chart, and the pattern is viewed at the monitor for fidelity.
Tempering Alarm - A tampering alarm is a sophisticated application found in some network cameras that can detect when a camera is being tampered with. The alarm can be triggered by potential acts of tampering, for instance if the camera lens is adjusted, obscured, or covered up.
Time Lapse VCR - A video recorder, most often in the VHS format, that can slow down the recording process and create a time lapse between recorded frames. This increases the amount of recording time on an individual tape. Unlike a standard VCR which has a maximum recoding time of 8 hours, time lapse recorders can record from 2 to 960 hours on a standard VHS tape. Recording speeds available on some Time Lapse VCR.
Time/date generator - is a device which generates time and a date, and superimposes it on the video signal.
Transmission Control Protoco(TCP) - The protocols, or conventions, that computers use to communicate over the Internet.
TV Line Resolution - the number of distinct horizontal lines, alternately black and white, which can theoretically be seen in a picture. Allows a buyer to judge the quality of any camera. Low resolution is between 300 and 380; medium resolution is between 400 and 480; and high resolution is 480 plus.
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U
Universal Serial Bus (USB) - A standard port that enables you to easily connect external devices (such as digital cameras, scanners, and mice) to a PC.
Upstream - The uploading of data from your PC to the Internet. ADSL has both upstream and downstream data rates.
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V
Varifocal lens - is a type of manual zoom lens with a small zoom ratio (ranging between 4mm to 12mm depending on brand). It is used when the focal length of the lens needs to be fine tuned to meet the requirements of the actual scene.
VCR Activator - A unit, when used with a PIR camera, that will automatically instruct your domestic video to record. After motion has stopped, the VCR Activator will stop your video recording.
Vertical Resolution (TVL) - The number of horizontal lines that can be seen in the reproduced image of a television pattern.
Video Amplifier - A wideband amplifier used for passing picture signals.
Video Band - The frequency band width utilized to transmit a composite video signal.
Video Capture Card - Computer cards installed on the motherboard to create a video recording computer.
Video Graphics Array (VGA) - The display standard for PC monitors. VGA outputs are compatible with PC monitors.
Video Motion Detection (VMD) - A method for detecting motion in a video image by checking to see if the pixels in the video image have changed.
Video Server - (In analog) A video server compresses video signal from analogue cameras to allow them to be viewed over a network such as a LAN or the internet. (In digital) A video server is a computer-based device dedicated to delivering video streams online. In terms of IP-based video surveillance, a video server converts video footage from analog security cameras into digital IP video streams. This allows users to incorporate existing analog cameras into an IP surveillance system.
Video Signal (Non-Composite) - The picture signal. A signal containing visual information and horizontal and vertical blanking (See also Composite Video Signal - but not sync)
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W
Wavelet - A mathematical codec useful in image compression. In the Internet, wavelet has been used to compress images to a greater extent than is generally possible with other methods such as JPEG or MPEG.
Web Server - A DVR or Software system with a built-in web server allows you to view cameras over an internet browser.
WDR (Wide Dynamic Range) Cameras - Wide Dynamic Range is a technology utilized by security cameras in order to balance out images that have a large dynamic range. An example of this situation would be if an indoor security camera were pointing towards a window or building entrance. During daytime, the image produced by the camera would be extremely washed out due to the high brightness of the incoming light. This effect is commonly seen in restaurants, stores, offices, and other buildings that have large windows or entrances.
Wired camera - A camera that transmits its signal via cable back to the recording/control device. Some wired cameras use composite cable (taking both the video and power signal) while some have separate power and video cables.
Wireless Camera - Wireless cameras allow the transmission of video and audio data to be transmitted to the receiver without having to run wires (using radio waves). Wireless cameras often have an option to power the camera via mains in which case there will be a lead from camera to power point.
Wireless network cameras - are able to connect to a network wirelessly, allowing for flexible installation in virtually any location. In general, wireless IP cameras are recommended for use in areas where the installation of cables isn't feasible, and for surveillance applications where cameras will be moved and repositioned regularly.
WPA (Wi-Fi Protected Access) - is a wireless encryption standard that indicates compliance with security protocol established by the Wi-Fi Alliance to secure wireless networks.
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Y
Y Signal - A signal transmitted in color television containing brightness information. This signal produces a black and white picture on a standard monochrome receiver. In a color picture it supplies fine detail and brightness information.
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Z
Zoom - Zoom functionality is available in many network camera models. It allows users to zero in on specific details and areas of a scene, and can often be controlled remotely.
Zoom Lens - An optical system of continuously variable focal length. The focal plane remains in a fixed position.
