Here you’ll find the answers to some of the most frequently asked questions about CCTV and the terminology used:
If you should need any further information our Technical Sales Team will be happy to help.
Please call +44 (0)1279 419913 or email your enquiry to:
Q. What is AGC?
A. Automatic Gain Control is an electronic circuit that automatically adjusts the Video amplitude under various lighting conditions. Note: if the AGC is set too high electronic noise can be introduced into picture making it appear grainy. AGC can be switched on and adjusted to preset levels.
Q What is ALC?
A Automatic Level Control compensates for bright spots in scene and allows details to be viewed in both dark and light areas.
Q What is Ambient Light?
A The general light level of the scene to be viewed.
Q. What is an Analogue Signal?
A. A signal (i.e. voltage or current) that varies continuously to match the scene being viewed by a camera. Note: A CCD camera produces an analogue video output signal.
Q. What is the Angle of View?
A. The amount you can alter the camera’s angle of view depends on the focal length of the lens fitted. You need to check the relevant lens angle charts to obtain this information.
Q. What is lens Aperture?
A. The centre of the lens that gathers light forms the scene. The size of the aperture, which is measured in ‘F’ stops*, is controlled by the iris. It is always better to have a lens with large aperture as this allows more light to pass through the optics.
* See below.
Q. What is Aspect Ratio?
A. A conventional CCTV system has an horizontal to vertical aspect ratio of 4:3. Note: many flat screen monitors have a Wide Screen aspect ratio of 16:10 which distorts the picture.
Q. What is Attenuation?
A. The loss of signal measured in decibels.
Q What is Automatic Iris – Auto Iris?
A. A lens that has an adjustable diaphragm that responds to varying levels of light and maintains a video amplitude to a pre-determined level. There are two types AI (Auto Iris) or DD (Direct Drive).
Q What is AWB?
A. Auto White Balance automatically adjusts the colour balance to maintain the white scene.
Q. What is Bandwidth?
A This represents the capacity of the transmission medium to carry data over a transmission line within a fixed period of time. Normally the larger the bandwidth the better the signal quality at the receiving end.
Q What is Baseband Video?
A Baseband is the complete composite video signal. It is not suitable for domestic television sets which require a modulated signal.
Q. What is BLC?
A Back Light Compensation is an electronic circuit that compensates for high background lighting and reduces the silhouette affect.
Q What is a BNC Connector?
The bayonet-fitting British Naval Connector is used extensively for transmitting video signals.
Q. What is a Bullet camera?
A A term to describe any CCTV camera that is cylindrical in shape.
Q What is a “C- Mount"?
A. The industry standard for a lens thread measuring one inch in diameter with 32 threads per inch. Other lens mounts are available such as CS mount and various board lens mounts. Please contact our Technical Sales Team for further information.
Q. What is a CCD?
A Sometimes known as an image sensor chip a Charge Coupled Device is a silicon, wafer thin, electronic device that is sensitive to light. They are available in various sizes – e.g. 1/2", 1/3" and 1/4" formats.
Q. What is CCIR?
A. The European Standard for a 625 line television system.
Q What is CCTV?
A A Closed Circuit Tele Vision system allows transmission of pictures via a “closed loop”. A typical system comprises a camera, video cable and monitor.
Q What is Chroma Burst?
A. This is a reference signal which allows cameras and monitors to produce a locked colour signal.
Q What is Chrominance?
A The part of the video signal that contains the colour information.
Q What is a Coaxial Cable?
A A cable with an inner conductor and an outer shield which is designed to carry high frequencies at a low loss.
Q What is Colour Saturation?
A The level of colour mix between colour and white. High saturation creates vivid colours.
Q What is the colour coding for Pecan camera cable connections?
A The majority of Pecan cameras use the following colour codes:-
Red 12v DC +
Yellow Video Signal
Grey/White Audio Signal
Visit the download area to check the relevant datasheet for confirmation.
Q What is Composite Video?
A. A signal that contains video, blanking and vertical/horizontal synchronising pulses. Video amplitude is 700mV and sync pulse amplitude is 300mV.
Q What is Compression?
A An electronic digital process that reduces the original signal. Common types are JPEG, MPEG and Wavelets.
Q What a DIP switch?
A A small on/off switch mounted onto a PCB to allow easy configuration.
Q What is Depth of Field?
A The amount of the scene that is in focus. If the iris is closed the depth of field increases. In poor lighting depth of field decreases.
Q What is a DVR?
A A Digital Video Recorder records video information in a digital format onto a computer hard disc drive or other digital media such as Compact Flash or SD card.
Q What is an ELC?
A An Electronic Light Control is an electronic circuit which compensates for varying light conditions on cameras which are not fitted with an Auto Iris lens. Note: the ELC must be selected for Fixed or Manual iris operation.
Q What is an “F” stop?
A Every lens has a quoted “F” stop or number. The smaller the “F” stop the more sensitive or “fast” the lens is - because more light is transmitted through the optics.
Q What is Fibre Optic Cable?
A A special cable that transmits light modulated by a video signal over long distances. This optical transmission is free from electrical noise and interference.
Q What is “Field”?
A A video frame has two fields - odd and even. A typical PAL CCTV system comprises 25 frames and 50 fields per second.
Q What is Field of View?
A The relationship between the width and height of the scene to be viewed. There are many variables determined by the focal length of lens, the sensor format and the distance to the objects.
Q What is Focal Length?
A The distance from the mid point of the lens to the sensor. The longer the focal length the narrower the field of view.
Q What is Hertz?
A A measurement of the frequency of signal in cycles per second.
Q What is IR?
A Infra Red is light energy which is red in colour, has a frequency between approximately 700 (nanometers) and 1mm and is outside the human visible spectrum. IR lighting is used in many 24/7 applications but is easily affected by adverse weather conditions such as rain, fog and moisture.
Q What is Illuminance?
A A measurement of light in lumens per square metre. The unit used is called ‘lux’.
Q What is an Integrated camera?
A A unit that contains a camera, lens and lighting in one “Integrated housing”.
Q What is IP rating?
A Ingress Protection is an index that defines the level of protection given against outside influences.
Q What is IR focus-shift?
A The difference in focus between daylight and infra red light. Note: check the specification of lenses on all TDN cameras for further information.
Q What is a JPEG?
A Joint Photographic Experts Group. A standard for image compression sometimes also used as a graphic image file format.
Q What is LED?
A A Light Emitting Diode frequently used when IR lighting is required.
Q What is Luminance?
A The part of the video signal that contains monochrome data.
Q What is MPEG?
A Moving Picture Experts Group is a standard for digital video and audio compression.
Q What is NTSC?
A The National Television System Committee is the standard used in North America for colour television systems. NTSC is 525 horizontal lines and 30 frames per second.
Q What is OSD?
A On Screen Display allows cameras to be easily set up using a simple menu on the display monitor.
Q What is PAL?
A Phase Alternate Line is the standard colour television system used in Europe, Australia, various parts of Africa and the Middle East comprising 625 horizontal lines and 25 frames per second.
Q What is a Photocell?
A A device that switches at a pre-determined light level. Often used to switch on IR lamps.
Q What is Pinhole Lens?
A A small lens with a tiny aperture which is mainly used in covert cameras.
Q What is a Pixel?
A A photo sensor on an image sensor that converts light to an electrical signal. The more pixels a sensor has, the higher the resolution.
Q What is RCA?
A The Radio Corporation of America phono plug or jack is used extensively for the transmission of video and audio signals.
Q What is Signal to Noise S/N ratio?
A The ratio between signal and noise expressed in decibels (dB). The higher the number the better the signal.
Q What is TDN?
A True Day Night cameras switch from colour to mono operation. They use a mechanical IR cut filter to ensure excellent colour reproduction during daylight and good sensitivity monochrome pictures at night.
Q What is TFT?
A A Thin Film Transistor is a type of Liquid Crystal Display.
Q What is TVL?
A TeleVision Line is the maximum number of changes between black and white. Normally measured across the picture width the higher the resolution the better the picture detail.
Q What is a Varifocal lens?
A A lens which can be manually adjusted within a range of focal lengths. Note: a varifocal lens needs to be re-focussed whenever the focal length is adjusted.
Q What is a Wavelet?
A A set of video compression mathematical functions which allow video
images to be compressed.
Q What is WDR?
A Wide Dynamic Range cameras allow scenes of high contrast to be viewed without “white out”.