Glossary A-D

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A

Access Control Cards

Plastic cards used to gain access to premises, usually associated with magnetic stripe and proximity cards.

Alphanumeric video generator (also text inserter)

A device for providing additional information, normally superimposed on a video signal.

Analog

A signal in which any level is represented by a directly proportional voltage; not digital.

Anti-aliasing

A procedure employed to eliminate or reduce (by smoothing and filtering) the aliasing effects.

Angle Of View

The maximum scene angle that can be seen through a lens.

Aperture

The lens opening that controls the amount of light reaching the pickup device (imager).

Artifacts

Undesirable elements or defects in a digital video picture.

Aspect Ratio

The ratio of the picture frame width to the picture frame height in standard TV systems. It is 4 units horizontal over 3 units vertical.

Aspherical Lens

A lens designed with a non spherical shape so that it refracts the light passing through it to either lower the lens aperture so that it passes more light or decreases barrel distortion on wide angle lenses.

Astigmatism

The uneven foreground and background blur that is in an image.

Attenuation

A decrease or loss in a signal. Reduction of signal magnitude (loss) normally measured in decibels.

Auto White Balance

Feature on color cameras whereby the camera constantly monitors the light and adjusts its color to maintain white areas.

Automatic Frequency Control (AFC)

An electronic circuit used whereby the frequency of an oscillator is automatically maintained within specified limits.

Automatic Gain Control (AGC)

An electronic circuit used by which the gain of a signal is automatically adjusted as a function of its input or other specified parameter.

Automatic Iris Lens

A lens in which the aperture automatically opens or closes to maintain proper light levels on the cameras pickup device.

B

Balun

This is a device used to match or transform an unbalanced coaxial cable to a balanced twisted pair system.


Bar Code

An array of machine-readable rectangular bars and spaces arranged in a specific way defined in international standards to represent letters, numbers and other human-readable symbols.

Biometrics

Biometrics utilize "something you are" to authenticate identification. This might include fingerprints, retina pattern, iris, hand geometry, vein patterns, voice password or signature dynamics. Biometrics can be used with a smart card to authenticate the user. The user's biometric information is stored on a smart card, the card is placed in a reader and a biometric scanner reads the information to match it against that on the card. This is a fast, accurate and highly secure form of user authentication.

B.L.C. (Back Light Compensation)

A feature of modern CCD cameras which electronically compensates for high background lighting to give detail which would normally be silhouetted.

Back Focus

The mechanical aligning of the imaging device with the focal point of the lens. Most important on zoom lenses to ensure the image stays in focus throughout the zoom range.

Band Width

The frequency range of a signal. The span that the information-bearing signal occupies or requires or the difference between the lowest and highest frequency of a band.

Base-Band Video

The frequency band occupied by the aggregate of the signals used to modulate a carrier before they combine with the carrier in the modulation process. In CCTV the majority of signals are in the baseband.

BER -Bit error rate

The ratio of received bits that are in error relative to the total number of bits received, used as a measure of noise induced distortion in a digital bit stream. BER is expressed as a power of 10. For example, a 1 bit error in 1 million bits is a BER of 10–6.

Bit rate

Bps = Bytes per second, bps = bits per second. The digital equivalent of bandwidth, bit rate is measured in bits per second. It is used to express the rate at which the compressed bit stream is transmitted. The higher the bit rate, the more information that can be carried.

Black Level

The level of the video signal that corresponds to the maximum limits of the black areas of the picture.

Blooming

The halation and defocusing effect that occurs around the bright areas of the picture (highlight) whenever there is an increase in the brightness intensity.

BNC

Video connector, the most commonly used in CCTV.

Byte

A digital word made of 8 bits (zeros and ones).

C

C Mount / CS Mount

The two industry standards for mounting a lens on a camera. The C-Mount lens has a 17.5mm flange back distance. The CS-Mount lens has a 12.5mm flange back distance.

C.C.I.R.

The European TV standard 625 lines 50 fields.

Camera

A device that translates light into a video image and transmits that image to a monitor for viewing. It contains the image sensor and other electronic circuitry to create a video signal.

Cathode Ray Tube (CRT)

The picture tube in a video monitor that can reproduce the picture image seen by the camera.

CATV

Short for Cable Access Television. The method for distributing RF signals via coaxial cable rather than radiated through the air.

CCD

Charged Coupled Device. This is a solid state semiconductor imaging device often referred to as an integrated circuit, chip or "imager." Solid state cameras are sometimes referred to as CCD cameras.

CCIR 601

An international standard (renamed ITU 601) for component digital television that was derived from the SMPTE RP1 25 and EBU 3246E standards. ITU 601 defines the sampling systems, matrix values and filter characteristics for Y, Cr, Cb and RGB component digital television. It establishes a 4:2:2 sampling
scheme at 13.5 MHz for the luminance channel and 6.75MHz for the chrominance channels with eight-bit digitizing for each channel. These sample frequencies were chosen because they work for both 525-line 60Hz and 625-line 50Hz component video systems. The term 4:2:2 refers to the ratio of the number of luminance channel samples to the number of chrominance channel samples; for every four luminance samples, the chrominance channels are each sampled twice. The Dl digital videotape format conforms to ITU 601.

CCIR 656

The international standard (renamed ITU 601) defining the electrical and mechanical interfaces for digital television equipment operating according to the ITU 601 standard. ITU 656 defines both the parallel and serial connector pin outs, as well as the blanking, sync and multiplexing schemes used in
both parallel and serial interfaces.

CCTV

The common abbreviation for Closed Circuit Television. A private or closed television system.

CCVE

Stands for closed circuit video equipment. An alternative acronym for CCTV.

CDS

Correlated double sampling. A technique used in the design of some CCD cameras that reduce the video signal noise generated by the chip.

CFA - Color filter array

A set of optical pixel filters used in single-chip color CCD cameras to produce the color components of a video signal.

CMOS

CMOS stands for charged metal oxide semiconductor. This is one type of camera image sensor which uses a charged metal surface to detect light and create a video image. CMOS technology is often smaller than CCD chips are currently capable of, so these cameras can often be quite miniature. Even the highest resolution CMOS cameras cannot compete with newer CCD imagers in resolution, sharpness, and low light performance.

Chrominance (C)

The part of the video signal corresponding to the color information.

Coaxial Cable

A type of shielded cable capable of carrying a wide range of frequencies with very low signal loss.

Coercivity

A technical term used to designate how strong a magnetic field must be to affect data encoded on a magnetic stripe. Coercivity is measured in Oersteds (Oe). Coercivity is the measure of how difficult it is to encode information in a magnetic stripe.

Color difference signal

A video color signal created by subtracting luminance and/or color information
from one of the primary color signals (red, green or blue). In the Beta cam color difference format, for example, the luminance (Y) and color difference components (R–Y and B–Y) are derived as follows:

Y = 0.3 Red + 0.59 Green + 0.11 Blue
R–Y = 0.7 Red – 0.59 Green – 0.11 Blue
B–Y = 0.89 Blue – 0.59 Green – 0.3 Red

The G-V color difference signal is not created because it can be reconstructed from the other three signals. Other color difference conventions include SMPTE, EBU-N1 0 and MII. Color difference signals should not be referred to as component video signals. That term is reserved for the RGB color components. In informal usage, the term “component video” is often used to mean color difference signals.

Color sub carrier

The 3.58MHz signal that carries color information. This signal is superimposed on the luminance level. Amplitude of the color sub carrier represents saturation and phase angle represents hue.

Color temperature

Indicates the hue of the color. It is derived from photography where the spectrum of colors is based upon a comparison of the hues produced when a black body (as in Physics) is heated from red through yellow to blue, which is the hottest. Color temperature measurements are expressed in
Kelvin.

Component Video

A video system containing three separate color component signals, either red/green/blue (RGB) or chroma/color difference (YCbCr, YPbPr, YUV), in analog or digital form. "Y" for luminance, "Cr" or "Pb for Chroma and red, and "Cb" or "Pb" for Chroma and blue. Component signals offer the maximum luminance and chrominance bandwidth.

Composite Video

Composite Video is the standard type of analog video signal utilized by most CCTV video cameras. This signal is plug and play compatible with most consumer television and VCR equipment. However, this type of video should not be confused with digital "component" inputs which may ALSO found on newer televisions and other home video equipment. A composite video signal has the correct phase rate, luminance, and chrominance information to be compatible with a particular video format such as NTSC, PAL, EIA, CCIR, etc.

Contrast

The range of light and dark values in a picture or the ratio between the maximum and the minimum brightness values.

D

Db (Decibel)

A measure of the power ratio of two signals. It is equal to ten times the logarithm of the ratio of the two the iris.

DC Type Lens

An auto-iris lens with internal circuit which receives voltage and a video signal from the camera to adjust signals.

Depth Of Field

The area in focus in front of and behind the subject.

Digital

The use of the binary numbers, one and zero, to represent a video, audio or data signal. Unlike analog signals which can degrade or have interference, digital signals maintain the quality of the original signal. Digital signals stored on computers, DVDs, CD, DVD's or other devices are exact duplicates of the original signal. When a digital signal falls below minimum thresholds, the signal is loss.

Digital Imaging

Scanning or otherwise capturing images which may be subsequently edited, filed, displayed or printed on a plastic card.

Digital Recording

This is the latest form of recording and is relatively new to the CCTV industry as a result is not the most economical method however it does have several advantages over the VCR analogue tape recorders. First of all it enables quick access to the desired

Digital Video Recorder (DVR)

This device is capable of accepting one or more video (and sometimes audio) input signals for recording onto digital storage media. A DVR is basically a computer specifically designed to gather and compress video into a digital video format for storage on a hard disk drive or other form of digital media.

Distribution Amplifier

A device that accepts a signal and increases the level for distribution over a large network

DLP

Abbreviation for Digital Light Processing. A Texas Instruments process of projecting video images using a light source reflecting off of an array of tens of thousands of microscopic mirrors. Each mirror represents a pixel and reflects light toward the lens for white and away from it for black, modulating in between for various shades of gray. Three-chip versions use separate arrays for the red, green, and blue colors. Single-chip arrays use a color-filter wheel that alternates each filter color in front of the mirror array at appropriate intervals.

Duplex (Multiplexer)

A multiplexer with two frame stores allowing it to show multi-screen pictures while performing time multiplex recording.

DVI (Digital Video Interface)

A video standard which provides a digital video signal which maximizes the video quality of modern digital monitors such as LCD and Plasma flat panel displays. Unlike conventional analog monitors, each pixel (dot) comprising the display is addressed separately, which results in the maximum possible clarity and color accuracy.

DVR

Abbreviation for Digital Video Recorder. A DVR is a video recording device that records on a hard disk drive, rather than on video tape or disc. DVRs can be incorporated into cable and satellite boxes, as well as an addition to a standalone DVD recorder. DVR use may, or may not, be paired with a paid subscription requirement. A DVR is also sometimes referred to as a PVR (Personal Video Recorder).

Dwell Time

The length of time a switcher displays one camera before sequencing to the next. Usually a variable setting.

Dynamic IP Address

A Dynamic IP address is a type of account from an ISP (internet service provider) where your computer or network is assigned an IP address that constantly changing and never remains the same. Also see IP Address and Static IP.

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