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Glossary - V
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- VDA
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Stands for Video Distribution Amplifier. A VDA is a device that typically has one input and multiple outputs, so you can display the same picture on multiple screens, such that interference to one output will not affect others.
- Vertical Shift Register
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The mechanism in CCD technology whereby charge is read out from the photosensors of an Interline Transfer or Frame Interline Transfer sensor.
- VHF
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Stands for Very High Frequency. A signal encompassing frequencies between 30 and 300 MHz. In television, VHF Band I uses frequencies between 45 MHz and 67 MHz, and between 180 MHz and 215 MHz for Band III. Band II is reserved for FM radio from 88 MHz to 108 MHz.
- VHS
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Stands for Video Home System, as proposed by JVC, a video recording format which is most often used in homes, but also in CCTV. It has its own limitations due to the concept itself, the speed of recording, the magnetic tapes used and the colour separation technique. Most of the CCTV equipment today supersede VHS resolution.
- Video equalisation corrector
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A device which corrects for unequal frequency losses and/or phase errors in the transmissions of a video signal.
- Video frame store
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A device which enables digital storage of one or more images for steady display on a video monitor.
- Video in-line amplifier
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A device providing amplification of a video signal.
- Video matrix switcher
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A device for switching more than one camera, VCR, video printer and similar, to more than one monitor, VCR, video printer and similar. Much more complex and more powerful than video switchers.
- Video monitor
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A device for converting a video signal into an image.
- Video printer
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A device for converting a video signal to a hard copy printout. It could be a monochrome (B/W) or colour. They come in different format sizes. Special paper is needed.
- Video signal
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An electrical signal containing all of the elements of the image produced by a camera or any other source of video information.
- Video switcher
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A device for switching more than one camera to one or more monitors manually, automatically or upon receipt of an alarm condition.
- VITS
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Video Insertion Test Signals. Special shaped electronic signals inserted in the "invisible" lines (in the case of PAL, lines 17, 18, 330 and 331) which are used to determine the quality of reception.
- VLF
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Very Low Frequency. Refers to the frequencies in the band between 10 and 30 kHz.
- VMD
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Video Motion Detector. A detection device generating an alarm condition in response to a change in the video signal, usually motion, but it can also be a change in light. Very practical in CCTV as the VMD analyses exactly what the camera "sees", ie. there are no blind spots.
- VS
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Vertical Sync.
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