Bob Dolph Answers Questions on Strapping Low-Voltage Cable, Audio Systems

I was told the other day by an inspector that I couldn’t use surface mount conduit to support low-voltage cabling. I have been strapping low-voltage cable to available conduit for years. What gives?
Well, according to the National Electrical Code (NEC), you cannot use conduit to support other exterior cabling strapped to it. However, in interviewing inspectors and AHJs in the past, I have been told that as long as this practice is not excessive, they will often allow it. So, as always, the local AHJ rules, even though the NEC says no. It is your call, but I would continue the practice cautiously and not consider it a handy shortcut.

I have an audio system question. I need to run the 8-ohm output of an amplifier into a 70V constant voltage audio system. Will it work?
Remember the old saying, “Low into high and you’ll get by?” You can run the 8-ohm output directly into the constant 70Vt system. Just make sure you have a large enough amplifier power. In this case, you will need a 500W amplifier. It is not as efficient as a 70V amplifier output, but it should work.


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About the Author


Bob is currently a Security Sales & Integration "Tech Talk" columnist and a contributing technical writer. Bob installed his first DIY home intercom system at the age of 13, and formally started his technology career as a Navy communication electronics technician during the Vietnam War. He then attended the Milwaukee School of Engineering and went on to complete a Security Management program at Milwaukee Area Technical College. Since 1976, Bob has served in a variety of technical, training and project management positions with organizations such ADT, Rollins, National Guardian, Lockheed Martin, American Alarm Supply, Sonitrol and Ingersoll Rand. Early in his career, Bob started and operated his own alarm dealership. He has also served as treasurer of the Wisconsin Burglar and Fire Alarm Association and on Security Industry Association (SIA) standards committees. Bob also provides media and training consulting to the security industry.

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