Varifocal Lens is one type of lens found on some of our cameras. This lens allows the user / installer to manually adjust the camera's field of view. Varifocal lenses can therefore be changed to provide wider viewing angles or narrower telephoto viewing angles. Because of their adjustability, varifocal lenses are great when a camera will serve more than one purpose or to ensure proper focus without first determining an exact fixed lens focal length. Varifocal lenses are also typically referred to as zoom lenses.
Variable bit rate Operation where the bit rate varies with time during the decoding of a compressed bit stream. Used in MPEG 1.
Vectorscope An instrument similar to an oscilloscope, that is used to check and/or align amplitude and phase of the three colour signals (RGB). It has a circular, rather than rectangular screen, to show the phase angles of the component colours.
Velocity of propagation Speed of signal transmission. In free space, electromagnetic waves travel at the speed of light (C). In coaxial cables, this speed is reduced by the dielectric material. Commonly expressed as percentage of the speed in free space i.e. 0.8C which is 0.8 x 3x108.
Vertical interval The portion of the video signal that occurs between the end of one field and the beginning of the next. During this time, the electron beams in the monitors are turned off (invisible) so that they can return from the bottom of the screen to the top to begin another scan. It is a time period where information can be inserted such as teletext, K codes and telemetry.
Vertical interval switcher A sequential or matrix switcher that switches from one camera to another exactly in the vertical interval, thus producing roll-free switching. This is possible only if the various camera sources are synchronized.
Vertical retrace The return of the electron beam to the top of a television picture tube screen or a camera pickup device target at the completion of the field scan.
Vertical shift register The mechanism in CCD technology whereby charge is read out from the photosensors of an interline transfer or frame interline transfer sensor.
Vertical sync pulse (also field sync pulse) A portion of the vertical blanking interval which is made up of blanking level lines of video. Synchronizes vertical scan of television receiver to composite video signal. Starts each frame at same vertical position. In total the vertical interval is 20 line long (CCIR & PAL).
VGA Video Graphics Array
VHS is the most common standard size for VCR cassettes. For normal VHS tape cassettes, there are three generally available recording lengths: T-120, T-160, and T-200. The number indicates the number of minutes recording on the tape in a VCR's highest tvres and fastest recording speed. However, the number of minutes attainable from such a tape is variable depending on the features of the VCR video recorder. For instance, most home VCR units have "extended play" or "slow play" modes to capture more time on a single tape. Many security VCRs also feature extended realtime recording and / or timelapse recording options to help conserve tapes. Video recording format used most often in homes but also in CCTV. Its limitations include the speed of recording, the magnetic tapes used and the color separation technique. Most of the CCTV equipment, today, exceeds VHS resolution.
VHF 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.
Video bandwidth The difference between the lowest and the highest signal frequency that a specific video signal can reach. The greater the video bandwidth, the better the quality of the picture. A video recorder that can reproduce a very broad video bandwidth generates a very detailed, high quality picture on the screen. The accepted bandwidth in CCTV is 5.5MHz for a colour signal.
Video Input Type refers to the type of video a device will accept for display, recording, etc. Our equipment (just like the majority of consumer video equipment most clients have at home) is made for compatibility with composite video. For use with S-Video, RGB component video, VGA, or other specialized / digital video formats, an adapter or converter may be required.
Video Input Plug indicates the plug size and configuration used for a device's video input. The most common types of plugs for composite video are BNC, RCA, and 1/8" mini.
Video Motion Detection is a feature of all DVR digital video recorders found on our Dvr. This is an advanced software feature which can detect motion in a camera's field of view and begin recording based on this motion detection. This type of detection can in most cases be adjusted in sensitivity. As well, a user can select and deselect areas in each camera's view for motion detection function. Advanced video motion detection erases the need for bulky and expensive PIR motion sensors.
Video Output Type refers to the type of video a camera or other device will output for display, recording, etc. on another device. Our equipment (just like the majority of consumer video equipment most clients have at home) is made for compatibility with composite video. For use with S-Video, RGB component video, VGA, or other specialized / digital video formats, an adapter or converter may be required.
Video Output Plug indicates the plug size and configuration used for a device's video output. The most common types of plugs for composite video are BNC, RCA, and 1/8" mini.
Video Quality is of course always subjective. However, when most users describe high quality video they are referring to a sharp and clear video image without distortion. Because of the high quality components and superior manufacturing of products found on Atss, these video devices feature amazing video quality. Consumers need to be aware that there are many quality differences available in the CCTV video surveillance industry.
Video Server (Network Video Server) is a device that accepts inputs from CCTV cameras using the PAL, composite video signal. It digitises the signal and then transmits images via a network, dialup or GSM connection. Advanced video servers have built-in video motion detection, and can buffer images while they are being uploaded to a remote server, where they are recorded. CCTV safe offer an advanced Video Server with all these features and more.
Video Switcher or Sequential Switcher. A device that allows the video signals from multiple cameras to be displayed on a monitor, or recorded on a VCR one at a time in sequence.
Video Distribution Amplifier (VDA) A special amplifier for buffering the video signal so that it can be supplied to a number of items of equipment at the same time. Each output will need to be individually terminated at 75 Ohms.
Video gain The amplification factor through any piece of equipment. Many loopthrough items are passive, i.e.. no gain.
Video equalization corrector (video equalizer) A device that corrects for the high frequency losses and/or phase errors in the transmission of a video signal along long lengths of cable. Video framestore. A device that enables digital storage of one or more images for a "frozen" display on a video monitor.
Video in-line amplifier A device providing amplification of a video signal.
Video matrix switcher (VMS) 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 simple sequential video switchers.
Video monitor A device for converting a video signal into an image.
Video printer A device to produce a hard copy printout from a video signal. It may be either a monochrome (B/W) or colour printer. They come in different format sizes and often special paper and inks are needed. Many computers now can be fitted with a video capture card, which means the print can be produced using a normal computer printer.
Video signal An electrical signal containing all of the elements of the image produced by a camera or any other video source.
Video switcher A device for switching more than one camera to one or more monitors manually, automatically or upon receipt of an alarm condition.
Video wall A video wall is a large screen made up of several monitors placed close to one another, so when viewed from a distance, they form a single large video screen or wall.
VLF Very Low Frequency. Refers to the frequencies in the band between 10 and 30 kHz.
VMD 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 change in light. Very difficult to set up for use externally but can be useful in carefully controlled situations. Modern VMD systems can learn the scene and ignore such things as tree and foliage movement.
VOD Video On Demand. A service that allows users to view whatever program they want whenever they want it with VCR-like control capability such as pause, fast forward and rewind
Voltage Requirements generally refers to the amount of input voltage required to safely and effpixelsly power an electronic device.. |
