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I received a CNB VCM-24VF to replace an existing camera. The existing camera is using a 12V DC power supply which according to the manual will work for this camera, however, it states that it should not be used over UTP. Can someone explain to me why I can use 24V AC but not 12V DC over UTP?

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The manual with the CNB is a generic one that they include with just about all their cameras, so there's no way to know for sure why they include that generic warning, but I suspect it's either because IR models (especially those with large numbers of LEDs) can be too much current draw for 12V over UTP (especially if you're only using one or two pairs for power), or because 12V cameras with shared power/video grounds can have ground-loop problems using baluns... either way, it's probably easier for them just say "don't do it" rather than try to spell out all the conditions under which it may or may not cause problems.


In any case... the VCM-24VF will work just fine with 12VDC over UTP - I have dozens of them running this way, including a few running two cameras over a single Cat5e (which means a single pair for power to each camera) at upwards of 150'. The 24VF will accept a wide range of AC and DC input voltage (if memory serves, they'll actually work with anything from 10-30V AC or DC), so voltage drop isn't generally a concern, and since they have internal regulators, the balun/ground-loop problem doesn't occur.

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