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FAQ about Security Systems > CCTV Glossary > Important definitions for the CCTV systems

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ActiveX

A Microsoft open technology for Windows-based applications. ActiveX controls can be downloaded as part of a Web document to add functionality to the ActiveX- enabled browser, e.g. Internet Explorer.

AF (Auto Focus)

An ability by which the camera lens automatically adjusts its focus on the captured subject.

Angle

The area of view, measured in degrees. It is the view that a lens can cover in practical usage. A short focal length has a wide-angle.

Aspect ratio

The ratio of width to height of a screen or video picture. Most TVs and monitors have a 4x3 aspect ration-- the screens are 4 units wide and 3 units high.

AutoIRIS

A special type of iris, is used to adjust the amount of enter light, electrically controlled by the camera.There are two main types of AutoIRIS - Video and DC IRIS. See also Video IRIS and DC IRIS.

Coaxial cable

It is an electrical cable that consists two conductors, separated by an insulating layer. It is used to transmitting analog video in a CCTV system.

CMOS

Complementary Metal-Oxide Semiconductor, one type of image sensor found in digital cameras.CMOS chips are easier and cheaper to make than CCDs but don't match the picture quality generally.

CCD

Charged Coupled Device, an electronic detector made of silicon that converts light energy into electronic signals. It is used in many digital cameras for image detection.

JPEG

Joint Photographic Experts Group; is an image compression format for images. Unlike other formats, it is a lossy compression technique.

Infrared (IR)

Infrared radiation is a radiation of a wavelength longer than visible light, but shorter than microwave radiation. The color cameras can detect the infrared radiation by the heat and capture it.It will filter the infrared radiation by IR-cut filter and prevent the distortion.Under low illuminance or night, the cameras will remove the filter and allow infrared radiation to hit the image sensor and produce images.

IP address

Internet Protocol address; is a unique number that devices use to identify and communicate with each other on a network, which uses the Internet Protocol standard.

IP Waterproof Rating (IP66 - IP68)

The IP rating means that product is protected against the ingress of solid object and water. Many cameras or camera housings are designed for outdoor use, and therefore need to be waterproof. The first digital is the protection against solids, and the second digital is the protection against water. Refer to the above table for details; E.g.,

IP66 - Total protected against dust and strong jets from all directions.
IP68 - Total protected against dust and long periods of immersion under pressure.

IR Cut filter

Infrared-radiation cut filer, is a color filter used in color CCD or CMOS, in order to block the infrared light and make the colors more realistic.

Interlacing

A process that divides each video frame into two fields. The odd numbered lines to be field one and all the even numbered lines to be field two.
Interlaced video uses two video fields to make a single frame of video.

IEEE 802.11

A group of standard wireless specifications developed by the IEEE. It defines a wireless interface between devices to manage packet traffic and supports speeds up to 2Mbps.

kbps

Kilobits per second, a unit of network connection speed. (1 kbps equals to 1,000 bits per second).

LED

Light Emitting Diode, a semiconductor used to convert information from electrical to optical form, typically as an indicator light.

Megapixel

Pixel element is used to display the images captured from digital cameras. The Megapixel is generally equal to one million pixels.

MPEG

Motion Picture Experts Group standard that specifies a variable rate compression algorithm that is used to compress full-motion image sequences at low data rates.

MPEG-4 Simple Profile

One kind of MPEG4 Profile, used to specify which method the MPEG4 decoder would support. It supports I-, PVOPs (frames),CIF resolution and 384 kbit/s. (at the L3 level). Refer to Wikipedia for details.

MJPEG(Motion JPEG)

Motion JPEG, is a video codec consisting of a sequence of individual JPEG images. The image quality is independent from the motion of the image that differs from MPEG video.

MAC address (Media Access Control address)

Media Access Control address; is one unique code assigned to a networking device. For example, the network card in a computer has its own MAC address.

NTSC

National Television Systems Committee; is the most popular video display standard in North America.NTSC uses 525 TV lines per frame and frame rate is 30 frames per second.

Optical Zoom

Optical zoom amplify the image size by adjusting the lens. It enlarges the subject without sacrificing resolution.

PAL (Phase Alternating Line)

Phase Alternating Line, is a video display standard used in Europe and certain other parts of the world.PAL uses 625 TV lines per frame and frame rate is 25 frames per second.

S/N ratio

The ratio of the value of the signal to that of the noise (expressed in decibels). The higher the number, the better.

TVL (TV Lines)

TV Lines is used to define the resolutions in analog video. The higher TVL value, the sharper the image.

VPN (Virtual Private Network)

Virtual Private Network; is a private communications network often used within a company.

Weather-proof

A protection for the camera from the adverse environmental conditions.

WDR [Wide Dynamic Range]

CCTV camera function to provide clear images even under back light circumstances where intensity of illumination can vary excessively, namely when there are both very bright and very dark areas simultaneously in the field of view of the camera. WDR enables the capture and display of both bright and dark areas in the same frame, in a way that there are details in both areas, i.e. bright areas are not saturated, and dark areas are not too dark. (Source http://en.wikipedia.org/wiki/Wide_dynamic_range)

W-LAN (Wireless LAN)

Wireless Local Area Network, a LAN that is connected via a wireless connection.