Camera-monitor:Which Type to Select?
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(Sponsored Links) Therefore, depending on the use and on personal preferences, one should have an idea of what to look for in a Camera-monitor when going to buy one or checking if it is possible to use surplus equipment available in house. In case of doubt, ask! Make sure that the Camera Monitor you select will work in fact with your other equipment to be linked together. Analog Display A TV set receives and manipulates video and audio signals either broadcast at radio frequency or conveyed along cables (Cable TV) over the UHF (Ultra High) and VHF (Very High) frequency bands. The color television monitor has a video decoder that can take the single composite video color signal, turn it into the three separate color signals and feed those to the color tube. On the contrary a CCTV monitor is able to accept only composite video signals and typically provides a higher number of lines of resolution displaying a better picture quality. As a Camera-monitor requires the signal information in analog form (continuous electrical signals or waves), most of the CRT (Cathode Ray Tubes) devices typically use analog connections. Camera monitors are meant to receive composite video signals directly through cable or through a short range radio transmission. See Video Signal Transmission. Therefore they do not make use of the TV tuning feature permitting to select the desired channel. However any unused TV set displaying a Video IN connection (that bypasses the radio frequency section of the TV set) can usually be connected to a camera for viewing the captured images, provided both are of the same standard (NTSC, PAL or SECAM). Size The size of the monitor is not critical but at least 14" would make viewing comfortable at a practical distance. It should be so located as to provide easy viewing to the observer. Note that all monitors generate heat: adequate ventilation and air conditioning should be provided, especially in a small room. Dedicated or Switchable Alternatively for a simple home surveillance system based on a few cameras, it may be nice to view multiple images simultaneously (multiplexed) on the same Camera-monitor or to examine any single camera image more closely. As multiplexed (smaller) images fill only a fraction of the full screen, this option may suggest the selection of a larger size Camera-monitor for easier viewing. Color vs. Black & White. The Camera-monitor resolution is a function of total number of lines available for displaying images. Lines of resolution refers to the total number of lines the camera or monitor is able to reproduce. The more lines on a screen, the better or sharper the video picture will appear. This issue is explained in some detail in the Fundamental Concepts page under the heading Resolution. A Camera-monitor can provide up to 1000 lines of resolution compared to an average of 300 lines of a television set. The more lines on a screen, the better or sharper the video picture will appear. It should be noted that this quality describes the overall resolving power of the whole system, reflecting the capability of the least resolution device connected in the surveillance system. However, as there is no accepted standard to test this value, the number of lines reported by a manufacturer as the resolution of a Camera monitor may be manipulated by using in the test high quality accessories (i.e. lenses etc.) to arrive at higher numbers than the consumer might be able to perceive with current quality devices. Generally a B&W Camera-monitor has a larger number of lines than corresponding color ones. High resolution Camera monitor is available in B&W and color: however one may say that a number of monitor lines largely exceeding that of the connected cameras would not help in providing a better resolution. For home surveillance purposes high resolution is probably not needed. Important Update All that has been written above became obsolete in the US, at least for what concerns broadcast TV, on February 17, 2009. On that date all the US 1700 analog television stations were shut down. Since then only digital TV will be available to the public. How will this affect Home Security users? Not much. All those having set up and operating an all analog self contained CCTV Home Surveillance system will not become aware of any change, at least as long as their system is up and working. Those going to purchase a new Camera-monitor will probably find that analog television sets become even cheaper than monitors, because there will be no request for obsolete sets. It is important to know that even brand new analog TV sets became useless in the US for watching TV programs after the above date. It is therefore necessary to understand the difference between analog and digital Camera Monitor even if one prefers to select the older analog screen. A Camera-monitor is also different from a computer display. Digital Computer Display To view the images on a computer screen one should first feed to a video grabber the analog output of a surveillance camera. Furthermore the computer screen resolution, expressed as the number of horizontal pixels by the number of vertical pixels, can be changed by the user, depending on the Operating System, by the following sequence or a similar one: If acceptable, this solution completely eliminates the need for an analog Camera-monitor, while at the same time sequestering the computer screen for this dedicated surveillance use. As explained elsewhere, see Camera Audio, it may not be legal to provide an audio channel to home surveillance cameras. Therefore there is no use for audio hardware (amplifiers, speakers) in the Camera-monitor. One such display that lacks audio capability is in general less expensive than another with audio capability.
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Click on this Logo NOW! Copyright © 2005, 2006, 2007, 2008, 2009, 2010, 2011 Camera-monitor is the device displaying the views captured by surveillance cameras. As an essential element of any home security system its characteristics should be defined with care. See this page for details... |
