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CCTV Terms


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

The most common question we are asked is "What is the difference between a DVR and an NVR? Both terms are used to describe security video recorders. DVR stands for "digital video recorder"" and NVR stands for "network video recorder". The main difference is, the term NVR is typically used to indicate a recorder that supports network or IP based cameras and uses network cable such as Cat6 to transmit the video. DVRs use coax cable to transmit video. The video below provides more detail.

CCTV stands for "Closed Circuit TV" and is often used to reference the security camera industry in general. It can be used to specifically refer to old analogy cameras systems and technologies as well.

In reference to CCTV, this refers to systems and components that use the standard NTSC/PAL video formats. Analog was the first technology and has been used since the early 1960's. The technology transmits video over Coax Cable, Rg59 or Rg6. The technology is in its twilight and will be eliminated when the last of the older systems die off. As the analog components fail they can now be replaced with new digital equipment that uses the same coax cable but transmits 4K video (our CVI series).

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 video recorder. The advantage is that you can follow the movement of an individual anywhere within the range of the camera. Most motion tracking cameras are 70-80% accurate.

Back focus:
A mechanical adjustment in a camera that moves the imaging device relative to the lens to compensate for different focal lengths. 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 or cat6 (rather than coax 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 (NVR, DVR, monitor, etc.). Baluns can be passive or active (with amplification). Passive distance can be up to 2,000 ft but keep in mind that only the video signal is transmitted and the camera would require local power.

This is the standard connector type used with coax cable. It provides an easy snap-on connection for a Rg59 or Rg6 coax cable. What BNC stands for is less clear. Some say it means British Naval Connector while others attribute it to the type and the inventor; Bayonet Neil Councilman.

Call Monitor:
This is a secondary monitor connected to a video recorder or multiplexer, etc. This is also called a Public Display Monitor or Spot Monitor. The video displayed is typically a single image. Some units provide multiple outputs. This feature is often used for public display monitors, such as the screens displaying your image as you are walking into a convenience store.

This is the basic video collection device that has many forms and configurations. They offer several different housing designs; PTZ dome design, vandal dome or turret design, and bullet style or (box cameras). These styles of cameras are offered in several technologies such as analog, CVI, TVI, AHD and IP.

Cat5 & Cat6 Cable:
This refers to the wire category of the 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. Several versions are offered and each is designed for specific applications. Some of the most popular for the CCTV industry are: Cat6e indoor network cable, Outdoor UV Rated Cable (Black or White), Direct Burial Cable.

CMS Software:
This is an acronym for Central Management Software. Recently other terms have been used to reference the same software such as UI (user interface) or PSS (personal surveillance software). They are all generic terms used to indicate the installable remote software packages provided by any NVR or DVR manufacturers. 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 a 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, as well as 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 H.264, H.265, M-JPEG and MPEG-4. Some manufacturers use proprietary compression methods that are usually modified versions of the standards.

Covert Camera:
A covert camera is not visible to every 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. Advanced features 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. Security Dealers come is all sizes and capabilities. They buy from manufacturers or distributors and design CCTV systems to meet individual customer needs.

DNS: (Domain Name System):
Matches Internet computer names to IP numbers. This allows you to type in the URL ( 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 to DHCP is to manually enter a static IP address for 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 when using IP cameras that connect 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 a 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 the video recorder. Digital zoom and optical zoom are two completely different features, the video below explains this at 1:40.

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 that have different parameter settings.

An acronym for Digital Video Recorder.

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.

Factory Defaults:
This term refers to the original menu settings of a device when it was shipped from the factory. When problems are encountered after changing menu settings, it is sometimes beneficial to restore the factory defaults 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 an NVR or DVR. They are also called "Thumb Drives" and "Memory Sticks".

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 more narrow the angle of view will be.

Frames or FPS (frames per second):
Fluid video is created by rapidly sequencing still frames images one after the other. 30 images sequenced within 1 second provides "live" fluid video.

H.264 & H.265:
These two video compression methods are now standards in the industry. They provide the highest quality video with the smallest file sizes. H.265 is the newest standard providing up to 60% more compression than H.264.

An acronym for Hard Disk Drive. Hard drives have evolved to support the huge demands of 4K video. A normal hard drive stressed under the work load of 4K video can commonly fail within 1-2 years. Western Digital has created a line of "Purple Hard Drives" specifically designed for the video surveillance industry. They can handle the huge work loads of multiple channels of streaming 4K video. The size of the hard drive needed for a video surveillance system is a factor of the number of cameras, the resolution, the frames per second and the number of stored days desired. It may sound complicated but, to simplify things for you, we have created a storage calculator that makes it easy to estimate the size of the hard drive that is optimal for your system. Give it a try!

Acronym for High Definition Multimedia Interface. This is a single cable connection used in consumer electronics that provides a high level of clarity. It is required to view 4K clarity. For CCTV systems, one "HDMI cable" from the NVR or DVR to a 4K flat screen is required to complete a true 4K system.

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.

Infra Red Light:
The wavelength of light produced below the visible part of the spectrum. Humans can’t see this light but security 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.

IP66 & IP67:
IP 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, such as IP66. This rating would mean that your outdoor dome enclosure is totally resistant to dust and water entry. IP67 is completely water tight.

Security Camera Weather Rating

IP Address:
This is the individual address of a 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:
Usually referring to "IP based video security cameras". They are IP network based rather than the traditional video signal used in broadcast and coax closed circuit systems. IP based is currently the industry standard.

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

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

An 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. Live video is produced with 30 frames per second video.

Megapixel refers to cameras with pixel content higher than NTSC/PAL formats. Current sizes of up to 12 megapixels are available. The size will continue to grow. Click here for more detail about "resolution & megapixels".

Motion Activated Alerts & Alarms:
Video motion alarms are triggered by recognizing changes in the pixels of an image. Intelligent processing monitors the pixels and, when movement patterns occur, the alert is generated. There is no physical connection causing the alarm condition.

(Motion Picture Experts Group): This video compression method is an improvement over M-JPEG as it provides smaller average usable file sizes.

N/O, N/C:
Acronyms for Normally Open and Normally Closed. This refers to alarm inputs/outputs and alarm devices. Most common alarm devices provide a dry contact closure to initiate a device such as a siren or light. Some devices are normally an open circuit that closes a switch on alarm while others do the opposite. Most NVRs & 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 appliance.

Acronym for Open Network Video Interface Forum. This is the IP standard data and communication format for surveillance and security cameras. It is a voluntary standard. Unfortunately many manufacturers deviate from the standard with certain software features to promote their brand or lock the customer into their cameras. This can causes unpredicted performance problems when different brands of equipment are used on the same system. The current version is ONVIF 2.6.

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

Phase Alternation Line; the European standard color television system, except for in France. PAL's image format is 4:3. When installing a new camera in North America, verify you have the camera set to NTSC and not PAL. If set to PAL, the equipment will not be in phase with the power and you will have a distorted and washed out image.

Player Software:
This is the generic term used to identify software that is used to review exported video in a standard PC. The many NVRs and DVRs requires this software to play the video on a PC and it is usually exported to the device along with the video. Our ProVue line of NVRs is different as they allow the video to be exported in MPEG4 format so that it can be played on any computer without a proprietary player.

Acronym for Power over Ethernet. This is a network device that provides power to IP cameras using Cat5 or Cat6 cable."PoE power units" have become very popular in the security industry as they offer several system design advantages that can save money and reduce installation labor using a distributive system design.

A preset position is an image view selected on a PTZ camera. The desired image position is saved and can be later recalled by selecting the preset number. When several presets are saved, the system can run the presets in sequence creating what is called "Custom Tours". The video below show the presets in action.

Privacy Zones:
This refers to the ability of a camera to mask parts of its normal viewing area to prevent the operator from viewing these areas. This can be in fixed or PTZ cameras. The intelligence for operating this feature is built into many cameras as well as our ProVue line of NVRs. The feature can be applied to any camera though the NVR.

Real-time recording:
There are several interpretations of this phrase. Most people refer to it as "full motion video" or "live" video which in the CCTV industry is 30 frames per second.

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

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 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, 4x4, 8x8 and any number of custom multi-screen divisions. The video below details the viewing options with our ProVue line of 4K surveillance recorders.

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. The term is also use to describe the most common type of hard drives "SATA Hard Drives".

In CCTV context, search refers to methods used to find video in a recorded database. Typical search methods are by time/date, alarm list or 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 power. This design simplifies the 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 and transmitted trough the 18 gauge wire in the Siamese cable.

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.

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

Acronym for Universal Serial Bus. This is standard PC hardware. It allows external devices to be easily connected to a PC, NVR, DVR, etc.

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, line cross, vehicle count, visitor ID, missing/found object, people count, etc.

Video Clip:
This is usually a short video sample that is saved from a database to document an issue. The video clip can be viewed on 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 NVR or DVR) but the video signal has been lost. This sends an alert to the operator, informing them of the video loss. This loss could be due to vandalism or to a component failure. Though, most likely it is due to a bad cable connection.

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

Acronym for Wide Dynamic Range. This refers to a high end feature of cameras. A camera viewing an image with very bright and dark sections will probably not show any detail in the dark areas. This is because the camera has 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) currently need significant improvement in reliability.