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Section A

IViewCameras - CCTV and Security Cameras

AC Adaptor – Also called a power supply. All CCTV devices needs power of some sort. Each device has its own power requirements (usually 12 volts with a minimum amperage). The power coming out of the wall (in the UK) is 240 DC. The adaptor converts the AC power to DC power and will adjust it to a specified amperage. The power supply should be included with each item - you usually don`t have to buy these separately.

AGC - Automatic Gain Control. A circuit for automatically controlling amplifier gain in order to maintain a constant output voltage with a varying input voltage within a predetermined range of input-to-output variation.

Alarm input - An input connection to a security VCR or DVR that triggers the unit to start recording if the alarm is triggered.

Analogue - There are two main ways of doing things electronically, analogue or digital. An analogue signal can be represented as a series of sine waves. The term originated because the modulation of the carrier wave is analogous to the fluctuations of the human voice or other sound that is being transmitted.

Angle of view - For security cameras, this refers to the angular range in degrees that you can focus the camera on without distorting the image. When focusing close up, you can generally see a wide angle of view. If the focus is distant, the angle of view is smaller or narrower.

Aperture - In television optics, it is the effective diameter of the lens that controls the amount of light reaching the photoconductive or photo emitting image pickup sensor.

Asymmetrical Digital Subscriber Line (ADSL) - A method for moving data over regular phone lines. An ADSL circuit is much faster than a regular phone connection, and the wires used are the same wires used for regular phone service. ADSL supports data rates of from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate). ADSL requires a special ADSL modem.

Audio/Video Interleave (AVI) - An AVI file is a sound and motion picture file that conforms to the Microsoft Windows Resource Interchange File Format (RIFF) specification. AVI files (which end with an .avi extension) require a special player that may be included with your web browser.

Auto Balance - A system for detecting errors in colour balance in white and black areas of the picture and automatically adjusting the white and black levels of both the red and blue signals as needed for correction.

Auto Iris - A lens in which the aperture automatically opens or closes to maintain proper light levels on the faceplate of the camera pickup device.

Automatic Brightness Control - In display devices, the self-acting mechanism which controls brightness of the device as a function of ambient light.

Automatic Gain Control - A process by which gain is automatically adjusted as a function of input or other specified parameter.

Automatic Iris Lens - A lens that automatically adjusts the amount of light reaching the imager.

Automatic Light Control - The process by which the illumination incident upon the face of a pickup device is automatically adjusted as a function of scene brightness.

Automatic White Balance - A feature on colour cameras that constantly monitors the light and adjusts its colour to maintain white areas.