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Beginner's Guide To Surveillance
Although there are many articles on CCTV and surveillance systems, most are for the professional integrator and most are for commercial, industrial or government applications. This brief article is designed to acquaint the average homeowner to some of the key concepts and terms that might be helpful for a simple home surveillance system.
The basic surveillance system is comprised of the camera, lens, and monitor, and if recorded video is needed, then a recording device, such as a VCR or a DVR. Let's first look at the camera.
The key items to know about the camera are whether indoor or outdoor application, amount of available light for the camera to see, needed resolution of the camera, and last, wireless or hard wire from the camera to the monitor.
Light levels for cameras are usually measured in Lux, which is a measurement of light energy on a surface. A typical office environment might have 500 Lux whereas a residential street lighting might be 0.5 - 3 Lux. Decent color cameras often will have a 2 Lux or lower rating and monochrome (B & W) cameras often under 1 Lux.
A great way to handle night vision problems is with IR lighting. IR LEDs, usually on the camera itself, provide illumination and if a color camera, at night, the camera will switch to monochrome and is, therefore, essentially a 0 Lux camera for the distance of the IR LEDs.
Resolution for cameras is expressed in TV horizontal lines. Standard resolution for a B & W camera is perhaps 380 TV lines and a high resolution might be 550 TV lines or higher. For color, standard resolution is a minimum of 330 TV lines and high resolution 480 TV lines or higher. Professionals need a 500 TVL or higher, perhaps, to read the number of a license plate on a moving car. However, for most home security applications 380 TVL is sufficient.
Two types of image sensors are used in cameras today, CCD and CMOS. They use different technologies and generally speaking, CCD sensors create higher quality and lower noise images then
CMOS sensors. On the other hand, CMOS cameras consume far less power and cost much less to manufacture. CMOS cameras are rapidly catching up to CCD cameras in terms of image quality.
The lens is important and the focal length of the lens tells you the field of view the camera will see at a particular distance. For example, with a 1/3 inch format camera and lens, a 2.8mm lens will see at 10 feet away a 17 ft wide and 13 ft high area at about an 80-degree angle. Using an 8mm lens for the same distance, the area is now only 6 ft wide and 4.5 high and the angle is 33 degrees. The smaller the focal length number is the wider the field of view becomes.
Wireless transmission is increasingly popular because government regulations have changed and allow systems without a license to transmit up to around 100 meters line of sight. This means maybe an average range of 25-30 meters indoors. Although many of these cameras can be battery powered, for permanent use a power supply is still needed. This means no wire is needed between the camera and the monitor, but you still need an outlet, typically, to plug the DC converter power supply in for the camera and the monitor will also need its own power supply. Still, for many homeowners this is far preferable than running RG59 coax throughout their home.
The monitor can be a dedicated professional CCTV monitor, or in the case of most home surveillance systems, just use one of the TVs already available. Most of today's TVs have multiple A/V inputs and outputs with RCA type of connections.
If recording is needed, again most homes have either a VCR or DVR available. However, home VCRs and DVRs are not designed for 24 hour per day recording, 365 days per year. For this type of recording need, it is best to buy a separate, professional unit designed for heavy-duty recording.
If more than one camera is used then a switcher or quad processor is often used to change between camera pictures one at a time, or to display up to four cameras at the same time on one screen. Remember what is seen on the monitor or TV is what is recorded.
Professional integrators today use multiple channel DVRs for
recording up to 32 cameras, or more, in one box with large hard drives and network capability. For most home surveillance applications, however, a quad processor with a VCR or single channel DVR is sufficient.
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Rca Rc59I Clock Radio with Ipod Dock
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