Glossary of Terms - CCTV
Two main methods exist for representing data in electronics - Analogue, and Digital. Analogue relates to a mechanism that represents data by measurement of a continuous physical variable. Analogue cameras are used most often in CCTV applications due to their relative inexpensiveness, compared to digital cameras. Other examples of analogue devices are time lapse video recorders, switchers and multiplexers. CCTV systems that consist of analogue devices are considered to be analogue systems.
This is when you can both see and hear what is happening through your monitoring system.
Auto Iris Control:
This is the name for a lens that allows aperture to automatically open or close in order to maintain good light levels on the faceplate of the CCTV camera pickup device.
Auto Gain Control:
This refers to an electronic circuit used and the gain of a signal is then automatically altered as a function of its input or another specified parameter.
The channel used on your TV to watch DVD's or operate games consoles.
Back light Compensation:
The ability of a camera to compensate in cases where a subject with a large amount of background light would otherwise be obscured by blooming or silhouetting.
BNC is a bayonet style connector for coaxial cable that's commonly used for CCTV installations.
A type of camera with a bullet like shape. Can be used inside or externally as they are usually IP rated. Some come with infrared lighting.
CCD stands for ‘Charge Coupled Device’, which is used as a type of image sensor. Commonly used in video equipment or portable camcorders as they use high quality sensors.
Closed Circuit Television. A television system used for private purposes and not for public or general broadcast.
CMOS stands for Complimentary Metal Oxide Semiconductor. This is used in another type of image sensor. CMOS sensors are commonly used in digital cameras and other low-powered images devices such as USB web cams as they use medium quality sensors. See also CCD.
This refers to a cable that has a central conductor, and is surrounded by a shield that shares the same axis. The shield can be made from a variety of materials such as, braided copper, or lapped foil. The cable that is normally used for regular CCTV installations is called RG59.
The act of compression involves taking an incoming signal or image, which can be analogue or digital, and restructuring the data so that it uses less resources to store and transmit.
Covert CCTV Camera:
One used where you don't want the person to know that they are being watched or recorded. Also known as 'hidden' cameras.
Day/Night CCTV Camera:
Regular camera with a highly sensitive CCD chip with the ability to capture quality imagery with very little light present – Can record colour images during daylight hours and switch to mono during darkness or low light levels. Not to be confused with Infra Red Cameras
The majority of CCTV cameras still remain to be analogue, however Digital Video Recorders (DVR) are fast becoming industry standard. Digital CCTV cameras are available but they still remain extremely expensive. The vast majority of new systems installed will be analogue CCTV cameras due to the cost of digital CCTV and DVR.
CCTV systems that include a DVR are however considered to be digital systems.
Do-It-Yourself security. The component can easily be installed without the help of professional installers.
A type of camera with a dome-like shape, can be supplied as a fixed camera or as a fully functioning camera. Some fixed are designed to be tamper-proof and vandal resistant, with high impact housings.
This refers to the ability to transfer data both in and out of a recorder at the same time - a full DVR can also continue recording images whilst previously recorded images are being watched.
Digital Video Recorder. A device that can record video signal digitally. This is normally on a large hard drive in the machine, because of this it is sometimes referred to as a hard disk recorder (HDR).
Field of View:
The visible area of a lens. With reference to CCTV security cameras this area will vary depending on the distance between the camera and the subject and the focal length of the camera lens being used.
The longer the Focal Length the narrower Angle of View, the shorter the Focal Length the wider the Angle of View. A wide angle of view will cover wide areas but provides very little recognition of a person not close to the camera.
Frames Per Second - in digital video applications, refers to the number of video images that can be captured, displayed, or recorded in a second. The human eye sees around 19 frames per second, the higher the number of frames per second recorded the less jerky recording appears
Fully Functional Dome Camera:
A dome camera with pan, tilt and zoom functions.
Hard Disk Drive.
Covering or container featured on some cameras designed to protect from it from the weather, often supplied with a built in heater to prevent condensation.
This is the light sensitive chip that can be found inside a digital camera. It can read levels of light & transform them into an image.
Infrared radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. The name infra-red means ''below-red'', with red being the colour of light that is visible with the longest wavelength. Through the use of IR LED's (Infra-red Light Emitting Diodes), or IR Lamps used for longer distances, as illumination for CCTV cameras that can see in infra-red light provides illumination needed in order to capture clear images in complete darkness of conditions of low lighting.
The Iris controls how much light is let into the camera lens.
Stands for "Joint Photographic Experts Group" and is a standard way of compressing images which works particularly well for photographic images.
A monitor that uses liquid-crystal display technology. A large number of laptops and notebook computers tend to use LCD displays as they only require low power.
Is a unit of light measurement. It refers to the amount of light required for a camera to capture a good image. Infrared cameras have very low lux. 0.01 Lux is about the light you will see from a quarter moon. The lower the number the higher the sensitivity.
A feature standard in most DVR's to only begin recording video if something in the image moves or changes. Useful as it saves a lot of hard drive space
MPEG (or MPG):
This is a standard used to compress audio and video files. It is called MPEG as it stands for "Motion Picture Experts Group" who designed the standard.
Pan Tilt & Zoom (PTZ):
A motorised CCTV camera mounting that is capable of moving both horizontally (pan) and vertically (tilt) and also has the ability to zoom in via electronic signals from a remote controller.
This refers to the ability of a DVR to record after a motion detection event has occurred for a specified duration of time after the event was triggered, regardless of whether the motion may have stopped.
The setting on DVR systems that is used for motion recording. When a DVR is set to record motion, it normally takes a second or so to begin recording once the motion has been triggered. Using pre-record, a buffer of previous frames prior to being triggered by motion is recorded to the drive, this allows the security camera to capture several seconds prior..
A device that is used for displaying 4 cameras simultaneously on a single monitor.
RCA AV Connector:
A plug and socket for a two-wire (signal and ground) coaxial cable that is widely used for connecting analogue audio and video.
Real Time Recording:
In digital video applications, 30 frames per second appears just like real-time. No jerkiness or hesitation appears in the video.
Refers to the sharpness and clarity of an image.
Signal to Noise Ratio; this number represents how much signal noise the camera can tolerate and still provide a good picture. The higher the number the better.
A switcher takes multiple camera inputs and will show them sequentially on the monitor. Unlike a quad it cannot display them all at once; however it will also allow you to select a single camera to view.
The frequency that video signals are sent wirelessly to a receiver that is connected directly to a TV or monitor.
Television Lines (TVL):
This measures the resolution of a video device. The higher the number the higher the resolution. Medium resolution is considered to be 380 TVL and 480 TVL or more is considered to be high resolution.
Time lapse Video Recorder:
A VCR that can be set up to slow down it's rate of recording rate to extend the length of time that can be recorded on to a standard tape to a maximum of 960 hours. This is made possible by recording one frame at set time intervals. The majority of units have an alarm input signal so that in the case of an alarm it can be automatically switched to real time mode.
Stands for “Thin Film Transistor”. These transistors are used in high-quality flat panel liquid-crystal displays (LCD’s). Displays using TFT-based displays use a transistor for each individual pixel on the screen.
A camera lens in which the focus is not fixed, it can be manually or automatically adjusted
Video Capture Card:
Computer cards that you can install on the motherboard of your own computer to create your own video recording computer. Not really recommended due to compatibility issues.
An increase in video signal power by an amplifier, expressed as the ratio of output to input. Also called amplification.
Also called camera inputs or channels - a connection in a video controller or recording device that you can plug a camera into. The more video inputs available on a device the more cameras you can connect to it.
Weather resistant cameras are suitable for use outdoors. They must be shielded from direct sun, rain, temperatures, snow and wind.
Wireless - Transmission Distance:
Outdoors - Approximately 330ft (100m) for open line of sight without obstruction. Indoors - Usually between 66ft (20m) and 100ft (30m), due to passing through ceilings and walls etc which may cause interference.
Wireless cameras allow video and audio data to be transmitted to the receiver using radio signals instead of having to run wires.
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