| Word | Description |
| A.I. (Auto Iris) | An electronic circuit fitted to the iris of a lens to help compensate for large changes in light levels. |
| A.L.C. (Automatic Level Control) | On AI lenses, also known as the peak/average control. Adjusting this control allows the auto iris circuitry to either take bright spots more into consideration (peak), bringing out detail in bright areas, or less into consideration (average) bringing out detail in shadows. |
| AC (Alternating Current) | An alternating current is an electric current whose direction reerses cyclically, as opposed to direct current (DC), whose direction remains constant. The usual waveform of an AC power circuit is a sine wave, as this results in the most efficient transmission of energy. Used generically, AC refers to the form in which electricity is delivered to businesses and homes. |
| ADSL | Asymmetric Digital Subscriber Line |
| ADSL (Asymmetrical Digital Subscriber Line) | A telephone line with uneven transmission rates; half the transmission can attain speeds up to 640 kbps; the other half can attain speeds of 2.048 Mbps or greater in the opposite direction. |
| AGC (Automatic Gain Control) | An electronic circuit that tries to keep signals at a constant level; more useful in cameras at low light levels. The higher the number the better, typical values 12 - 20dB i.e. a gain of approx 4x - 10x. |
| Ah | Ampere hours. e.g. 1A for 6 hours = 6Ah. Always de-rate the battery capacity by 66% |
| Alarming | The ability of CCTV equipment to respond to an input signal, normally a simple switch closure. The response varies depending on equipment type, most common is for switcher to 'hold' on the camera corresponding to the alarm input. |
| Ambient Light Level | Background or general light level of a given area. |
| Analogue | A signal in which any level is represented by a directly proportional voltage; not digital. |
| Angle of View | This is what alters (not the focal length) when you use a lens designed for one format on another format. It decreases with format size. |
| Aperture | The 'opening' of a lens, a measure of its light gathering capability. Relative Aperture is a ratio between its focal length and effective aperture, measured in F numbers, generally the lower the better. |
| Auto Back Focus | The function to adjust flange back by moving the CCD position. This is useful for installation and upon colour to B/W switching. |
| Auto White Balance | Feature on colour cameras whereby the camera constantly monitors the light and adjusts its colour to maintain white areas. |
| Auto-terminating | Feature whereby the equipment automatically selects the correct termination depending on whether the video output BNC is connected. |
| Auto-tracking | A function which controls PTZ to chase a moving object with image recognition and image processing software. Advanced auto tracking for WV-CW970 series is a more accurate Auto tracking with template matching algorithm which processes shape, colour and contrast of the object. |