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- A/D
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Also known as just AD or A2D. This refers to a Analog to Digital converter. An example of an A2D is on a DVR board. The analog signal from a camera is converted to digital format for the computer to store/analyze.
- Aberration
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Term used in optics. This refers to anything which affects the fidelity of an image in respect to the original scene.
- AC
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Alternating current or AC electricity is different from the DC electricity you get from batteries, in that it moves back and forth instead of flowing directly through the wire.
- Activity Detection
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Also known as Motion Detection. Refers to how some multiplexers/DVR's have the built in capability to detect movement within the cameras field of view. This is used to improving recording efficiency.
- ADC
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Analog to Digital Conversion. It is the first stage in which an electronic device processes a signal into a digital format. The signal can be video, audio, control output or other.
- AGC
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Automatic Gain Control. A part of an electronic circuit which regulates a voltage level to fall within a predetermined margin. Feedback is provided to control the level.
- ALC
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Automatic Light Control. Similar to the function of back light compensation in photography. It is part of the electronics of an automatic iris lens.
- Aliasing
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Is sampled data interference. This can happen in CCD image projection of high spatial frequencies. It can be lessened by a method known as optical low-pass filtering. Aliasing is also known as Moire patterning.
- Alphanumeric video generator
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Also known as 'Text inserted'. This is a device which will superimpose text onto an image being displayed. This can range from a few characters to a full screen.
- Amplitude
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The maximum value of a varying wave form.
- Analog Signal
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Representation of data by continously varying quantities. An analog electrical signal has a different value of volts or amperes for electrical representation of the original excitement (sound, light, ...) within the dynamic range of the system.
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