AGC: See Automatic Gain Control
Alarm Input: An input signal that can enable an alarm trigger event, examples; start recording, generate audible alert, send email.
Analogue: A signal whose voltage level varies. For example Analogue Video in the UK (PAL CCIR Format) is a 1 volt peak to peak signal; the video component (the top 0.7 volt of the signal) varies according to the brightness of the image. 0.3 volt is black while 1 volt is white. The PAL standard has a limited resolution; horizontal resolution typically 330 TVL to 700 TVL is the number of voltage reference pints across the image.
Analytics: Software video image post processing enabling data collection or extrapolation for example Facial Recognition, Footfall, ANPR and a wide range of intrusion and motion detetion.
Angle of view: For CCTV cameras, refers to the angular range in degrees that you can focus the camera lens. The angle of view for a particular lens varies depending in the camera imager size. Lens manufacturers will quote angles of view for the standard imager size. The larger the angle of view the smaller individual objects will appear in the image, wide angle lenses, typically 4mm will give an overview while focal lenses over 12mm will provide a zoomed in image (based on 1/3 inch CCD)
ANPR: Software based Automatic Number Plate Reading or Recognition from a video image, live, still or recorded
Aperture: A function of the lens, an iris similar to the human eye is used to adjust the (opening) aperture of the lens, the wider the aperture the more light will pass though. When setting up a camera and lens, the distance the imager is set to is critical to maintain good focus. The lens needs to be set to the widest aperture before adjusting this setting. See Depth of field.
Auto Iris: A function of a CCTV camera lens in which the aperture automatically opens or closes to maintain proper light levels through the lens to the imager device. Two main types exist.
- DD Direct Drive: The camera controls the lens motors directly.
- AI Video Drive: The electronics to monitor the video are built into the lens.
Auto White Balance: AWB The camera will automatically correct colour based on a known point of reference. Some cameras require this reference setting at time of initial installation. Different settings are used depending on source light, for example sunlight, fluorescent tubes, sodium street lighting.
Automatic Brightness Control: ABC Automatically controls the level of brightness of a monitor or video image from a camera.
Automatic Gain Control: AGC An internal electronic circuit that automatically controls amplifier gain in order to produce a constant output. AGC can cause additional noise in an image in low light conditions. With AGC turned off a cameras image can be very dark when light levels drop.
Back Light Compensation: An image processing feature on most modern analogue and IP CCD cameras which electronically compensates for high background lighting to give detail. Allows processing of images with a light background, persons entering though a doorway lit from outside for example.
Bandwidth: The available capacity of a transmission path.
- Analogue CCTV: The capacity of the link or cable to sustain the Video Transmission, the higher the camera TVL the greater the bandwidth requirement. Loss in bandwidth will affect camera resolution.
- Digital CCTV: The available transmission space on an IP circuit. The amount of sustained IP data traffic the link can sustain. The greater the bandwidth, the more digital video that can be sent in a given amount of time, this can be higher frame rates or resolution.
Binary: A base 2, number system which is represented by 0's and 1's. Commonly also referred to as bits. 8 bits make up a byte and 1024 bytes make up a Kilobyte. If we have an 8 bit binary number we can represent any value up to 255 of FF in hexadecimal, 1111 1111 in binary representing 128 + 64 + 32 + 16 + 8 + 4 +2 +1. Binary switches are often used to address CCTV devices.
Blooming: The defocusing or over brightness of regions of the picture caused by the an excessive level of light to part of the image, can be caused by headlights. In a camera, the sensor element saturates which causes widening of the spatial representation of a spot light source.
|BNC connector: Is a type of connector used to interconnect two coaxial cables or connect a cable with other CCTV components. Comes in variants specific for cable types and sizes and always best to use the mechanical crimp versions.|
Brightness: The level of processed light in an image, this can be adjusted on a monitor or by post digital processing. Luminance is the correct electronic engineering term ,which has also been called brightness.)
- Analogue: In television system use, a device having a band-pass greater than the band of a single VHF television channel.
- IP: Provision of internet service typically over standard telephone lines ADSL.
Byte: A unit of data consisting of 8 bits, used to store data, sometimes shown as a hexadecimal or binary number. With 8 bits it is possible to store a number from;
- Hexadecimal 00 to FF
- Binary 0000 0000 to 1111 1111
- Decimal 0 to 255
|Category (CAT) Cable: Four pair twisted data cable that is capable of transmitting IP and voice data at high speeds. CAT 5e and CAT 6 cable is commonly used for voice and data applications.|
CCD: See Charge Coupled Device
CCTV: A closed loop surveillance system consisting of cameras, recording and monitoring equipment connected over a "closed" or dedicated cabling or transmission system. Used for visual monitoring, public safety, health and safety and security applications. Also used extensively in industry for plant monitoring and control, automated quality assessment and site security.
C Mount: A television camera lens mount of the 16 mm format, 1 inch in diameter with 32 threads per inch. Not commonly used anymore although many of the Town Centre lenses from major manufactures are still C mount and require an adapter ring for CS mount cameras.
CCTV: Common abbreviation for Closed-Circuit Television.
Charge Coupled Device: CCD image sensor, a scanning semiconductor matrix array that enables the transfer of light and colour into electronic format. Early CCD imagers suffered from image bleed across the sensor often seen as streaks or lines in the image in bright conditions.
CMOS: Complementary Metal Oxide Semiconductor. Similar to a CCD, it is also used to detect light for conversion into an electronic signal. Commonly used in modern IP HD CCTV cameras while CCD devices are more common in analogue cameras.
Coaxial Cable: A shielded cable with an outer shield core and centre signal carrying conductor. Commonly used to transmit analogue CCTV signals.
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 algorithms include h264, Wavelet, Mpeg4 & Jpeg. Codecs are used to encoder analogue video signals into digital streams.
|Colour Burst: Part of the UK PAL video standard, this is a reference signal sent from the camera that allows the receiving equipment to lock onto a set frequency and enable the correct reproduction of the colour components within the image.|
Colour Saturation: The degree to which a colour is free of white light.
Composite Video Signal: The combined picture signal, including brightness, colour, contrast together with vertical and horizontal blanking and synchronisation signals.
- Analogue: The reduction in gain at one level of a picture signal with respect to the gain at another level of the same signal.
- Digital: The amount of the image data is "squeezed" higher compression can lead to image content losses or perceived blurring.
CS-Mount: C & CS Mount cameras are designed to accommodate a separate custom lens to suit the surviellance application. The lens can be removed, exchanged or replaced. CS mount has become the normal mounting for modern CCTV cameras with C-Mount lenses requiring a small adapter ring to be fitted between the lens and a CS mount camera. CS lenses cannot be used on C-Mount cameras.