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Basic Terms

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Let’s clear up some of the confusion about a few basic terms used in the surveillance industry.

You will see the terms DVR and NVR used to describe a video recorder. DVR stands for digital video recorder and NVR stands for network video recorder. Both perform the same functions and offer the same features. The only real difference is the term NVR is typically used to indicate a recorder that supports network or IP based cameras.

CCTV stands for closed circuit TV and is the term used to reference one of the main three technologies on the market which is analog surveillance cameras.

Below are shown a few terms used to describe the more popular styles of camera housings. While the housing and mounting options for each type are different, often the electronics and performance are identical. Typically indoor and outdoor versions of the cameras are available.

Basic CCTV terms

Other Common Terms:

In reference to CCTV, this refers to systems and components that use the standard NTSC/PAL composite video formats. Digital refers to devices that use pixel formats. The definitions become blurred when you consider that DVRs convert the analog signal into digital form to process the images internally, they convert back to analog to output to other devices. Details aside, many people refer to analog as old technology and digital as the new technology.

Automatic iris (Auto Iris):
A lens that adjusts automatically to allow the right amount of light to fall on the imaging device. There is a tiny motor and amplifier built in which receives a control signal from the camera to maintain a constant one volt peak to peak (1.0 Vp-p) video level.

Auto Tracking:
This refers to the ability of a PTZ camera to sense movement in the image and follow the movement wherever it goes. The actual intelligence for the function can be in the dome or in the DVR. The advantage is that you can follow the movement of an individual anywhere within the range of the camera. This comes under the heading of video analytics.

Back focus:
A mechanical adjustment in a camera that moves the imaging device relative to the lens to compensate for different focal lengths of lenses. This is important when a zoom lens is installed.

Balun: (Video balun):
This is a device that allows video to travel over twisted pair wire (rather than coax RJ59 cable). This device matches the impedances of the different signals. Balun stands for balanced-unbalanced. A balun is required at the camera and at the receiving device (DVR, monitor, etc.). Baluns can be passive or active (with amplification). Passive distance can be up to 1,000 ft. Active can be up to 3,000 or more. Count on less than half that distance with a DVR.

This is the standard connector type used in CCTV. It provides an easy snap-on connection for a coax cable. What BNC stands for is less clear. Some say it means British Naval Connector. Others attribute it to the type and the inventor; Bayonet Neil Councilman.

Call Monitor:
This is a secondary monitor connected to a DVR, Multiplexer, etc. This is also called a Spot Monitor. The video displayed is typically a single image. Some units provide multiple outputs. Cameo: Refers to an individual video image in a multi-screen display.

This is the basic video collection device that has many forms and configurations. Some are: box cameras (require a separate lens) bullet cameras (slim line all in one construction) dome camera (all in one in a dome design) PTZ camera (mounted on a PTZ platform device) PTZ dome (all in one package). An IP camera can be any of these and connect directly to a network.

C-Mount /CS-Mount Lenses:
C-Mount cameras and lenses were the first used in CCTV applications. The lens screws directly into the camera providing a distance of 17.5mm between the back of the lens and the imager. Current CS lenses are smaller and better suited for smaller cameras. The lens to imager distance is 12.5mm. A 5mm spacer called a C-ring, or C-mount is used with CS lenses to bring the lens to imager distance to 17.5mm.

CAT-5 Cable:
This refers to category-five cable. This is the typical cable wiring used in Ethernet networks. The cable contains four sets of twisted pair wires. The end connectors are RJ-45 connectors. CCD: Charge Coupled Device: It is light sensitive and forms the imaging device of most modern cameras. Size is measured diagonally and can be ¼” 1/3,” or ½."

Acronym for Complementary Metal Oxide Semiconductor. This type of IC (Integrated Circuit) technology is used in a wide range of analog circuits. CMOS is used for camera imaging. CMOS cameras were originally low in quality but improvements have been made to the point where they can compete with CCDs quality wise in many applications.

CMS Software:
This is an acronym for Central Management Software. This is a generic term used to indicate the installable remote software packages provided by any DVR manufacturer. Each manufacturer has a specific name for their CMS product.

This stands for Compressor/de-compressor. Some people call it encoder/decoder. This refers to the software that compresses and decompresses video.

Composite Video:
The complete visual wave form of the color video signal composed of chrominance and luminance picture information; blanking pedestal; field, line, and color sync pulses; and field equalizing pulses. More simply for CCTV purposes it contains the video signal and horizontal and vertical sync pulses on a single wire.

Video must be compressed in size in order to make it manageable in the record and remote transmit functions. Typical compression standards include M-JPEG, MPEG-4 and H.264. Some DVR manufacturers use proprietary compression methods that are usually modified versions of the standards.

Covert Camera:
A covert camera is not visible to the operator of the system. It is intentionally obscured from view and often used for surveillance of employees. An authorized operator with the proper password privileges can view the camera and recorded information.

"Composite Video Interface" is a new technology that allows for HD video to be transmitted over RG59 or RG6 coax cable. The term is used to describe the electronics and format of specific cameras and DVRs.

Day/Night Operation:
This refers to cameras that are capable of providing usable images at night by changing camera parameters to work more efficiently in low light. A basic example of day/night operation is the use of IR LEDs within the camera housing. Some very inexpensive cameras can provide usable images in total darkness. More sophisticated changes in more expensive cameras include switching the camera to black and white mode at night and reducing the image capture rate to allow more light to reach the imager.

In reference to CCTV, this is a generic term used to indicate individuals or companies that sell products to end users. Dealers come is all sizes and capabilities. They buy from manufacturers or distributors and design CCTV systems to meet individual customer needs. See “All you wanted to know about sales channels” for more details on the distribution process at www.compaircctv.com.

DNS: (Domain Name System):
Matches Internet computer names to IP numbers. This allows you to type in the URL (www.abc.com) instead of the IP address (

This is an acronym for Dynamic Host Configuration Protocol. This is a function that allows a network to automatically assign an IP address to a PC when the user logs on to the system. All devices on a network require an IP address. DHCP does this automatically. The alternative is to manually enter a static IP address in each device.

In CCTV, digital refers to devices that operate in pixel formats. Analog video devices use traditional NTSC and PAL formats. The lines of difference are blurred when you consider the analog signal is converted to digital and back again (often several times) within a traditional CCTV system. Pure end-to-end digital video is achieved using IP cameras through a network to NVRs and LCD monitors.

Digital Zoom:
This refers to enlarging a portion of an image by adding additional pixels within the image to fill the larger area. It makes the picture area larger at the expense of video quality. The intelligence for this feature can be in a camera or a DVR.

Acronym for Digital Signal Processor. DSP chips compress video freeing the CPU processor for other tasks. This increases compression capabilities at an additional cost.

Dual Stream:
This term is typically used to indicate a device capable of providing two different video compression methods. An example is a DVR that shows live video in M-JPEG and transmits to the remote software using MPEG-4. IP cameras often have selectable (dual stream) transmit capability. This may sometimes refers to two streams of the same compression method with different parameter settings.

An acronym for Digital Video Recorder.

An acronym for Digital Video Disk. This is the standard media used for PCs and movies.

Dynamic IP Address:
This refers to IP addresses that are automatically assigned to a network device when the user logs on to the system. See DHCP.

Embedded (DVR):
This is a manufacturer designed hardware platform for a DVR. It may share many functions with a traditional PC platform but it is a proprietary design that is unique to an individual manufacturer.

Factory Defaults:
This term refers to the initial menu settings of a device when it was shipped from the factory. When problems are encountered after changing menu settings it sometimes helps to restore the factory settings and start over.

Field of View:
This is the entire visible area of the image produced by the camera/lens.

Flash Drive:
A small USB memory device. Connect it to a USB port to import and export files. These devices are commonly used to export video from a DVR, upgrade firmware, etc. These are also called Thumb Drives.

Focal length:
The distance between the secondary principal point in the lens and the plane of the imaging device. The longer the focal length, the narrower is the angle of view.

The combination of two interlaced fields. The frame frequency is half the field frequency.

(File Transfer Protocol): Transfer documents between different types of computers.

This video compression method is an improvement over earlier formats (JPEG, MPEG-4) providing smaller average usable file sizes. See M-JPEG, MPEG-4 and H.264.

An acronym for High Definition Closed Circuit Television. This is an emerging new standard for sending video over standard RG-59 coax cable. One purpose of the standard is to take advantage of HD monitors and provide the clearest live picture possible. The standard requires modified hardware in cameras, DVRs and monitors. This is expected to be available early 2010. This sounds like a local live improvement but recording and sending the data through the Internet will require compression to be effective. We’ll see the results when it is available at trade shows.

An acronym for Hard Disk Drive.

Acronym for High Definition Multimedia Interface. This is a single cable connection used in consumer electronics providing a high level of clarity. This type of connection is beginning to show up in CCTV products.

Home Position:
This refers to PTZ cameras. The camera will return to a preset position after a selected period of inactivity. The preset position is usually preset #1. This feature ensures that the dome returns to a known position after an operator has moved it from the home position.

Hybrid refers to combinations of analog and IP video solutions. Originally this meant connecting analog cameras to video encoders for connection to an NVR. More recent Hybrid systems are a combination DVR/NVR allowing both analog (BNC) and Ethernet connected IP cameras.

Infra Red Light:
The wavelength of light produced below the visible part of the spectrum. Humans can’t see this light but cameras can. IR cameras use Infra Red LEDs to light an area and provide usable (black and white) images in what appears to humans to be total darkness.

The other IP. This one stands for Ingress Protection. It is a measure of the ability of an enclosure to resist dust and water. It is expressed (usually) as two numbers as in IP66. This rating would mean your outdoor dome enclosure is totally resistant to dust and water entry. Some of these claims are overstated (like air holes in the dome skin when it’s rated as wind driven waterproof). “Google” IP rating system for details on the levels of protection and their ratings.

IP Address:
This is the individual address of the computer. IP addresses are 32-bit binary numbers (all ones and zeros). This is fine for computers. Humans need an easier way to express the address. Each binary octet is expressed as a number between zero and 255. An example of an IP address is

IP Cameras:
These are IP based video cameras using IP networking as their basis rather than the traditional video signal used in broadcast and closed circuit systems.

An acronym for Infra Red. IR remotes typically control video devices (TVs, DVRs, etc.).

IR Camera:
Refers to cameras that have IR LEDs installed that turn on in low light providing a usable image in even total darkness. The effectiveness and distance varies widely based on the number of LEDs and overall quality of the camera.

IR Cut Filter:
IR light can distort colors in CCD and CMOS cameras. An IR filter is often used in cameras to filter out IR light during bright daylight conditions. An IR cut filter is automatically removed at low light to allow the camera to take advantage of IR light in lower light conditions. The camera usually switches to black and white operation at this time since B/W works better than color in low light. Iris: The mechanism that can be adjusted to vary the amount of light falling on the imaging device.

This is an acronym for Internet Service Provider. ISPs provide your connection to the Internet.

KVM Switch:
This is a switching device that allows one operator to control multiple PCs (DVRs, NVRs, etc.) using a single monitor mouse and keyboard. KVM stands for Keyboard, Video and Mouse. Systems can range from two and four unit options up to hundreds of units.

An acronym for Local Area Network. This could be as small as a two computer system, or, it could incorporate hundreds of users in a campus environment. It is local in that there is a direct wire connection between all parts of the network.

Liquid Crystal Display. An LCD is a flat-screen slim profile video display.

A LED is a Light Emitting Diode.

Live Video:
Live displays current activity. This can be at the camera location or at a remote site connected to the cameras through the Internet.

Loop Out:
This term refers to the additional BNC connectors installed for the purpose connecting the incoming video to additional devices. You will see these installed on many CCTV products.

Megapixel refers to cameras with pixel content higher than NTSC/PAL formats. Current sizes of up to 10 megapixels are available. The size will continue to grow. If you want to estimate the megapixel size used in security video next year just check the pixel size of consumer point and shoot cameras today.

Megapixel Lens:
Megapixel imagers have more pixels than standard imagers. A standard lens can’t focus light fine enough to resolve to a single pixel in megapixel formats. Megapixel lens have additional optical elements that allow light to focus on individual pixels. You will see the difference if you test the same camera with both lenses. The megapixel advantage can be lost with a less effective lens.

Motion Alarms:
Video motion alarms are triggered by recognizing changes in the video image. There is no physical connection causing the alarm condition.

(Motion Picture Experts Group): This video compression method is an improvement over M-JPEG providing smaller average usable file sizes. See M-JPEG, MPEG-4 and H.264.

Multiplexer (Multiplexor):
An electronic system that can accept a number of camera inputs and record them virtually simultaneously. They can also provide multi screen displays with four, nine, sixteen etc. cameras on the screen at once. Multiplexers can be used to transmit multiple pictures down a single video line whether it is a coaxial cable, microwave, infrared link etc. This requires a multiplexer at each end of the line.

Network Camera:
This refers to a network based camera. An IP camera can connect to an NVR. You can see the video with the NVR remote software. You can also connect directly to the network camera through a browser connection.

N/O, N/C:
Acronyms for Normally Open and Normally Closed. This refers alarm inputs/outputs and alarm devices. Most common alarm devices provide a contact closure to initiate the alarm. Some devices are normally an open circuit that closes a switch on alarm and others do the opposite. Most DVRs will accommodate either type with a menu selection.

National Television Systems Committee of the Electronics Industries Association (EIA) which prepared the NTSC format specifications approved by the Federal Communications Commission, for US commercial color broadcasting. `NTSC' also refers to a color television format having 525 scan lines, a field frequency of 60 Hz, a broadcast bandwidth of 4 MHz, line frequency of 15.75 KHz, frame frequency of 1/30 of a second, and a color subcarrier frequency of 3.58 MHz.

This is an acronym for Network Video Recorder. An NVR is a server hardware platform with proprietary video recording software installed. NVRs are designed to operate with IP cameras providing an all-digital configuration.

Acronym for Open Network Video Interface Forum. This is a growing standard for IP camera interface.

Optical Zoom:
This is the normal zoom capability of a variable focal lens. Example: A 5mm to 50mm zoom lens can be positioned any distance with no loss in video quality. By comparison, digital zoom enlarges the image but reduces the quality.

Acronym for On Screen Display.

OSI model:
OSI (Open Systems Interconnection), are the rules for network communication that the TCP/IP protocol carries out.

Phase Alternation Line; the European standard color television system, except for France. PAL's image format is 4:3, 625 lines, 50 Hz and 4 MHz video bandwidth with a total 8 MHz of video channel width. Pan Tilt Zoom (PTZ): A device that can be remotely controlled to provide both vertical and horizontal movement for a camera, with zoom. This is a movable mechanical base for a camera.

PC based DVR:
This is a DVR that is based on a standard PC hardware platform. There may be several proprietary components installed but the unit is primarily a PC with some modifications as opposed to a unique proprietary design.

Picture element. This is the smallest software addressable point on the image. The number of pixels in an image is measured horizontally first, then vertical (ex. 320x240).

Player Software:
This is the generic term used to identify software used to review exported DVR video in a standard PC. The proprietary DVR video format requires this software to play the video in a PC and it is usually exported to the device along with the video. Some manufacturers require you to install the player on your PC. Others run directly from the device (thumb drive, DVD, etc.).

Acronym for Power over Ethernet. This is a network device that provides power to a device using one of the CAT-5 cable twisted pairs. This is an installation advantage eliminating the need for a locally installed AC outlet.

An acronym for Point Of Sale. This usually refers to cash register data.

Pre Alarm:
In record on alarm only mode a DVR hard drive is not recording until an alarm is encountered. Some number of seconds or minutes prior to the alarm event can be recovered from a software buffer that is continuously overwriting itself. The video recovered from prior to the alarm is called Pre Alarm.

Post Alarm:
In record on alarm only mode a DVR can be set to record for a specific amount of time when an alarm is encountered. This time period after the alarm is called Post Alarm.

A preset position is an image view selected on a PTZ camera. The desired image position is saved and later recalled by selecting the preset number.

Privacy Zones:
This refers to the ability of a camera to mask parts of its normal viewing area to prevent the operator from viewing the protected areas. This can be in fixed cameras or in PTZ cameras. The intelligence for operating this feature can be included in a dome, a DVR or in a Matrix switch.

In CCTV context a protocol is the command set used to control one device from another. An example is that each manufacture develops their own code to send commands to PTZ domes. This is why you see so many options for camera control in DVRs. The protocol is the software element. The hardware element is RS-422, RS-485, etc.

In CCTV context proprietary indicates a non standard method of accomplishing something. This may be good or bad depending on the results. Some proprietary software solutions were developed by manufacturers before the current standards were implemented. Some are attempts to intentionally circumvent the ability to work with other manufacturer’s equipment. Most were just developed separately with no thought of how anyone else approached the same issue.

PTZ Dome:
A fully contained PTZ mechanism and camera installed in the same dome housing. QSG: Acronym for Quick Start Guide. A QSG is a short manual or pamphlet shipped with a product to assist the installer/operator in completing the initial installation.

Quad screen:
Display where 4 cameras are viewed on the same screen, each camera image occupying a quarter of the display area. Quad screens can be seen in devices with any number of camera inputs. The quad screen is just one of several multi-screen formats available.

RAID is an acronym for Redundant Array of Independent Drives. There are several different levels of RAID devices. The key is that if one of the drives fails, the information from that device is retained in the remaining drives. The different RAID levels range from storing all information in two separate locations, to using software gymnastics to share information on all drives so that any single drive failure will not allow any loss of data.

RCA Jack:
This is a standard connection used for audio. These connections are typically used for audio in CCTV.

Real-time recording:
There are several interpretations of this phrase. Most people refer to it as full motion video, just like TV (30ips in NTSC). Some call it real time even if the update rate is slower.

Record Duration:
In CCTV context record duration refers to the amount of time that a DVR will record before writing over the database with newer information.

Analog video resolution is based on viewing a test pattern and determining the “lines of resolution” number by how well you can differentiate a series of converging lines before the black and white lines fade to gray. This is very subjective and rarely accurate. This method depends on the other equipment used to be a higher quality than the tested device.

Digital resolution is the same as the pixel count. Using the analog test pattern method the resolution number will always be smaller than the pixel count.

This is the hardware device that provides a gateway to the Internet.

Scene illumination:
The density of light falling on the area to be viewed. For best results the ratio of the lightest to the darkest areas should not be more than a factor of two.

Screen Formats:
Viewing multiple cameras on a single monitor screen. Typical formats are full, 2x2, 3x3, 4x4 and any number of multiple screen divisions.

Screen splitter:
A term usually used for a device that can combine the views from two cameras on a single screen. Normally the camera syncs need to be locked together.

Acronym for Serial Advanced Technology Attachment. This is the cable that connects a PC motherboard to a disk drive or optical drive. It is a thin round cable providing serial communication. This is a newer technology than traditional parallel connections (ribbon cables). So you must know what type of drive each DVR requires.

In CCTV context search refers to methods used to find video in a recorded database. Typical search methods are by time/date, alarm list, smart search by video movement.

Siamese Cable:
This is a dual cable combining RG-59 video cable and an 18 gauge wire suitable for providing 12VDC or 24VAC power. This design simplifies installation of cameras. There is no need for a locally installed AC outlet at the camera location. Power is usually provided from a power distribution box at the control end.

Spot Monitor:
This is a secondary monitor connected to a DVR, Multiplexer, etc. This is also called a Call Monitor. The video displayed is typically a single image. Some units provide multiple outputs.

Static IP Address:
This is the name given to a manually entered IP address. In large networks IP addresses are usually automatically assigned by DHCP.

Type of video signal used in the SVHS videotape format. S-video transmits luminance and color portions separately, using multiple wires, thus avoiding the color encoding process and its inevitable loss of picture quality. This provides the video and sync signals on different wires.

Technical Support:
This refers to the organization and individuals that provide after sale support for installation and repair of products and systems.

Thermal Camera:
Thermal cameras don’t see light, they see heat. Providing a black and white image the camera can detect the body heat of an individual in the image. These are night vision cameras that can highlight an individual hiding in the bushes because of the heat difference. These are very expensive cameras with value for specific purposes.

Thumb Drive:
A small USB memory device. Connect it to a USB port to import and export files. These devices are commonly used to export video from a DVR, upgrade firmware, etc. These are also called Flash Drives.

Refers to PTZ control: You can select a series of cameras, Presets and Patterns into a tour. This will switch from one camera, preset or pattern to another in the order and for the time selected. The result is a tour (the name is derived from a guard tour where the guard physically goes from location to location) of video from a central location.

Acronym for Universal Serial Bus. This is standard PC hardware. It allows external devices to be easily connected to a PC, DVR, etc. Connected devices are typically hard drives, CD/DVDs and flash drives. UTC: This is an acronym for Up-The-Coax. This refers to sending telemetry information (PTZ control data) to a PTZ device on the same coax cable that provides the video. The data is transferred during the Vertical Blanking Interval (that wide black line you might see on a rolling image) and does not interfere with the video display.

Varifocal Lens:
This is a lens with a manually adjusted focal length. The field of view can be adjusted easily after the camera is installed. This simplifies installation with one lens type accommodating multiple locations.

Video Analytics:
This is the generic term used to identify any number of software based video tools used to make determinations based on the changing video content of a camera. A few examples of video analytics are: Auto tracking, motion exception, missing/found object, people count, etc.

Video Clip:
This is a (usually) short video saved from a database to document an issue. The video clip can be reviewed in a PC and maintained as a record of the incident. A video clip is often provided to the police to investigate an incident and/or used as evidence in a court case.

Video Loss:
This term refers to cameras that were once an active part of the system (connected to a DVR) and the video signal has been lost. This provides an alarm to alert the operator to the video lost situation. This loss could be due to vandalism or to a component failure. Most likely it is due to a bad cable connection.

Video Motion Detection:
A method of detecting movement in the view of the camera by the electronic analysis of the change in picture contrast.

Acronym for Wide Dynamic Range. This refers to cameras. This is a high end feature. A camera viewing an image with very bright and very dark sections will probably not show any detail in the dark areas as the camera is adjusted to tone down the bright areas. With WDR the camera view will be much improved showing detail in both light and dark areas. This feature also provides better image detail in low light conditions.

This refers to any device that can operate without the need for installing wires. High priced wireless systems have become very reliable. The low priced variety (the ones that would sell in typical low end CCTV applications,) need improvement in the reliability area.

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