CCTV Glossary Of Terms Part 2



This is a signaling device, either visual or audio based. For example, wireless annunciators use infrared beams that trigger an audible signal when interrupted, and can be used for security or retail purposes.


The Aperture is the opening of a lens that controls the amount of light let into the camera. The size of the Aperture is controlled by the iris adjustment. By increasing the stop number less light is permitted to pass into the camera. 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.

Aperture Correction

Compensation for the loss in sharpness of detail because of the finite dimensions of the image elements or the dot-pitch of the monitor.

Aperture Scale

The aperture scale is referred to as an F-number. Examples are F1, F1 .4, F2, F2.8, F4, etc.

Armor Dome Camera

Armor Dome refers to a hi-impact reinforced polycarbonate dome casing designed to resist vandalism on this brand of camera.

ARP (Address Resolution Protocol)

ARP is a method determining a host’s Ethernet address from its Internet address. The network receives the ARP request, and then names the IP address. Next, the machine at this address returns its physical address so the information can be sent to it. If supported by all hosts, Internet addresses can be independent of Ethernet addresses.

Aspect Ratio

The ratio of width to height for the frame of the televised picture. 4:3 for standard systems, 5:4 for 1K x 1K, and 16:9 for HDTV.


A type of lens in which the spherical surface has been slightly altered to reduce spherical aberration. This type of lens generally allows wide angle viewing with relatively low distortion.

Asynchronous Data

Most common for of data, where date is passed without any clocks or timing information, uses start and stop bits for synchronization.

AT Commands

A protocol between a modem and terminal equipment for autodialing and configuration of the modem.


In general terms, a reduction in signal strength.

Auto Balance

A system for detecting errors in color 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 Electronic Shutter

A CCTV camera feature that allows the camera to compensate for moderate light changes in indoor applications without the use of Auto Iris Lenses.

Auto Iris Control

A lens which allows the Aperture to automatically open or close to maintain proper light levels on the faceplate of the camera pickup device.

Auto Light Range

The range of light, e.g., sunlight to moonlight, over which a TV camera is capable of automatically operating at specified output.

Auto White Balance

A feature on color cameras that constantly monitors the light and adjusts its color to maintain white areas.

Automatic Brightness Control

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

Automatic Frequency

An arrangement whereby the frequency of an oscillator is automatically maintained within specified limits.

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.

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