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- D/A
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Also known as DA and D2A. Refers to Digital to Analog conversion. Is the opposite of A/D.
- Dark current
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Leakage signal from a CCD sensor in the absence of incident light.
- Dark Noise
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Noise caused by the random(quantum) nature of the dark current.
- dB
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Decibel. A logarithmic ratio of two signals or values, usually refers to power, but also voltage and current. When power is calculated the logarithm is multiplied by 10, while for current and voltage by 20.
- DC
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Direct Current. A current that flows in only one direction, as opposed to AC.
- Depth of field
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The area in front of and behind the object in focus which appears sharp on the screen. The depth of field increases with the decrease of the focal length, ie. the shorter the focal length the bigger the depth of field. The depth of field is always bigger behind the objects in focus.
- Dielectric
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An insulating(non-conductive) material.
- Digital signal
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An electronic signal where every different value from the real life excitation (sound, light, ...) has a different value of binary combinations(words) which represent the analog signal.
- DIN
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Deutsche Industrie-Normen. Germany's standard.
- DMD
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Digital Micro-mirror Device. A new video projection technology that uses chips with a large number of miniature mirrors, whose projection angle can be controlled with digital precision.
- DSP
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Digital Signal Processing. It usually refers to the electronic circuit section of a device capable of processing digital signals.
- Duplex
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A communication system that carries information in both directions is called a duplex system. In CCTV, duplex is often used to describe the type of multiplexer that can perform two functions simultaneously, recording in multiplex mode and playback in multiplex mode. It can also refer to duplex communication between a matrix switcher and a PTZ site driver, for example.
- DV - Mini (Digital Video)
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A new format for audio and video recording on small camcorders, adopted by the majority of camcorder manufacturers. Video and sound are recorded in a digital format on a small cassette(66X48X12mm) superseding S-VHS and Hi 8 quality.
- D-VHS
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A new standard proposed by JVC for recording digital signals on a VHS video recorder.
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