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TROUBLESHOOTING HYBRID SURVEILLANCE SYSTEMS FOR DUMIES Spectrum Analyzers more popular. Included on this list are power over Ethernet (PoE) network cameras that use 48VDC. What does this bring to the table? DC-powered devices use a true power supply, which means the voltage is rectifi ed and fi ltered whereas AC-input cameras use what is known as step-down voltage transformers. In AC, any noise that is present at the input of the transformer also appears at the output. In sum, the use of DC-powered cameras will help reduce noise situations in the future. CASE NO. 4: RFI AS A CULPRIT A quick look at the troubleshooting example depicted in Figure 4 does not require much thought before radio frequency (or microwave) interference comes to mind. T is is one of the most diffi cult problems to prevent and cure in video surveillance. In many cases fi nding the source could be next to impossible. Figure 4: RF Interference Part 4 of 4 that aff ects a video signal due to either electromagnetic induction or electromagnetic radiation emitted from an external source. T ese problems can be constant or they can randomly occur depending on the source of the interference. How does one RF (or microwave) interference is one of the most difficult problems to prevent and cure in video surveillance. Sometimes, finding the source can be next to impossible. Interference problems are on the rise. If we follow the same procedures and ask the right questions it will not take too long to determine that this interference is caused by radio frequencies. Whether you want to call it RFI or EMI, the result is a very unusable image on the screen. Electromagnetic interference or radio frequency interference is a disturbance A6 / SECURITYSALES.COM / OCTOBER 2012 troubleshoot and cure these problems? We previously stated that if the interference was gray or black in nature that the problem was being induced into the transmission media; if white, the interference was probably induced via the equipment's power source. In the case of RF, we have to add one more statement. If the RF penetrates the camera electronics, it will also produce grayish lines throughout the image. So, how to troubleshoot this problem? Let's start at the basics. For starters, fi nding the frequency of the interference would be a help. However, even if the frequency of the RF interference is known, fi nding Special test equipment called spectrum ana- lyzers can pinpoint frequencies at fault. But they can be expensive and trying to locate the problem source can still be a nightmare. the source may be a challenge. Most RF problems are generated by unlicensed frequencies (see Part III of this "D.U.M.I.E.S. " series for more info on wireless). Special test equipment, known as a spectrum analyzer, could pinpoint the frequency at fault. However, these units can be expensive and after identifying the frequency trying to locate that source could become a nightmare. A simpler approach in trying to solve this problem may be accomplished by asking the right questions. First, is this a new or old system? If it's the latter, what if any changes have been made to the overall system? Review other equipment located in the security room such as mobile communications, wireless networks, FIND IT ON THE WEB Visit the Educational Tools section at securitysales.com/dumies to access nine years' of "D.U.M.I.E.S." archives.