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Networks, switchs, power amplifier, cameras etc

August 6, 2015

I support a camera system that has many cameras over a network.  Sometimes cameras, individual ones, go off line.  Meaning they still show up in the system, but do not actually show anything.  While investigating this scenario yesterday, I walked around with one of our network tecs and the guy from the company who sold the hardware.  When a camera is down, follow these steps to try to bring back on line.

First – ensure the camera is getting power.  the camera is plugged into our network.  Look at the network drop, where the camera plugs into, and see if there is a number or something designating that drop location, like A15.  Next, find where that drop (the ethernet cable) enters the network – where does it plug in?  Which network switch box does it plug into?  We have a bunch of these *closets in our buildings.  Each closet contains lots of switch boxes which allow devices, like computers, copiers or cameras to be plugged into the network.  Once you find the closet – find the matching drop number, like A15.

In our case, the cameras are getting their data and power over the same line (cable) this is called a POE .  Power over Ethernet.  I think what actually happens is the cable coming from the camera plugs into a switch device – that has two connections for that drop, like A15.  So cable A15 plugs into the data in port on the power injector (PowerDsine 3501G) and then back out from the data and power out port  – back into the switch box.


Makes sense on a highly conceptual level.  This way, each device on the network does not need a separate power connection.

Yesterday – the power injector failed.  The power cable coming from the switch to the injector failed – at least it seemed to.  It indicated, via a yellow light, rather than a healthy green one, that something had failed physically in the device.  Once the device was replaced – the camera came back on line.

Moral of the story?  Networks are a little complicated and offer multiple fail points.  This problem was not software related, at all.


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