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I have a PTZ Security Camera that requires PoE+ (PoE class 4, IEEE802.3at). It requires 30 watt. I have an existing switch that only provides standard PoE/PSE 802.3af at a max of 15.4 watts. My question is whether I can us a PoE Injector such as the Veracity Outsource Plus POE+ injector in line to power my camera? In my proposed configuration, the Ethernet cable would come out of the existing standard POE Switch (15 watt max), through the POE plus injector and on to the camera. Would this cause too much wattage in the line since the switch that is upstream of the POE injector is POE also? Thank you!

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Yes, you can use an appropriate (ie. camera-compliant) injector even if the switch already provides PoE. If the injector has two identical sockets (instead of a socket and plug) be VERY careful to connect the unpowered socket to the switch, not the other way around, because you may blow the switch and the injector.

Every injector is basically an isolation transformer with central taps on one of the sides to inject DC, so even if you place 5 injectors in series, only the last one will really inject DC to the cable. If you then place 5 "receive" injectors in series on the same cable, only the first one will provide power, the rest will not be powered.

  • A simplified version of what filo has said is: PoE is only enabled when a device indicates that it supports PoE. The injector will never request PoE and thus PoE on that port, at the switch, will never be enabled. – Mark Henderson Mar 15 '16 at 11:01

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