Thursday, May 21, 2009
Video Surveillance Introduction - Part 1
At A Glance
Security is a big concern nowadays, with many people fearing this recession will bring higher crime rates. How can you help to protect your home or business? A CCTV (Closed Circuit Television) system is a good start. Let Discount Low Voltage help you make the right decision on what's best for you.
A CCTV system consists of a DVR, cameras and a monitor. Connect these three components together with the correct wire (see Coax or UTP) and a power supply for a do-it-yourself CCTV system. It's that easy.
Let's Talk DVR's
Digital Video Recorders (DVR's) were a huge step forward in video surveillance. Before the introduction of DVR's, you were forced to use VCR's with time-lapse capability. You'd program them to record "x" amount of Frames Per Second (FPS); a lower frame rate allowing more video to fit onto a single VHS tape. Recording higher FPS on VHS can get expensive very quick. In addition, VCR's only record one channel of video. For multiple cameras, you had to connect them to a multiplexer, which split the screen into 4,9, or 16 segments. But that's all in the past now. Let's get back to the good stuff. DVR's are essentially computers that record video to hard drives. They cost much less than their equivalent in VHS and can record multiple cameras. Depending on how many FPS you have it set for, they can record for days, weeks, even months on end. Many even have DVD burners built in so you can record the footage onto a DVD and keep it for future reference.
Not sure how many FPS to record? 24 FPS is considered "real time", while even 12 FPS looks close to real time. Many security installers use 7.5 FPS as the standard recording rate. To get this number, we take the recording rate of the DVR and divide it by the number of cameras you want to use. For example, a 16 channel DVR with a recording rate of 120 FPS, means each camera will have 7.5 FPS (120/16=7.5). If you buy a DVR with a recording rate of 480 FPS, those 16 cameras now have a rate of 30 frames per second (480/16=30). This is going to look very clean and flow nicely when viewing. If you want to view the cameras from your computer, you will need a PC based DVR. This allows you to access the DVR remotely from any computer in the world.
Check back next week for part 2 of this 3 part article. We will cover camera options and what's best for your particular application