POE – Power Over Ethernet

POE & POE Products

POE (Power over Ethernet) technology is now very mature and still expanding in uses.

MasTec started writing about POE five or so years back.

POE is made possible by the injecting DC Power intosome of the 8 wire in an Ethernet Cable

There are two types of POE

Mid-span: +48VDC is delivered across the Ethernet cable using the unused pins (4, 5, 7 & amp; 8).

End-span: +48VDC is delivered on on the same pins used for data (1,2,3 and 6).

At the far end of the Ethernet Cable an Etherent DC Splitter which brings out the DC and passes through the Ethernet data. The Splitters convert the POE voltage to standard voltages such as 48, 24, 18, 12 or 5 VDC.

It is possible to pump quite a lot of power down an ethernet cable > 100 watts and still have reliability in DC supply.

So imagine you are setting up video survellliance. All the cameras are 12VDC and TCP Gigabit Ethernet for the image data. Just plug the camera into the splitter for the DC power and the ethernet cable and you are done. You do not need to be near AC power to set up the camera, offering great placement freedom.

Usually POE is a high DC voltage > 24, sometimes much higher > 55 VDC.

This injection usually takes place at the Ethernet Switch or with a POE Injector product.

However now there are Computers and PACs that do the DC Power injecting also.

The same is true of course for DAQ systems that have ethernet data connections, see some of the manufacturerss in the list of suppliers