We are using passive PoE injectors and long ethernet cables. 

[[Image(power-ranges.png, 400px,right)]]
Below a reference table for the voltages ranges of the hardware we use:
||= '''Item''' =||= '''Low''' =||= '''High''' =||= '''Max Consumption''' =||
|| alix2d13    ||  7V || 20V ||  5.0W ||
|| NS5, M5, M2 ||  9V || 24V ||  8.0W ||
|| MS M2-Loco  ||  9V || 24V ||  5.5W ||
|| Bullet5M    || 10V || 24V ||  6.0W ||
|| airCam      ||  9V || 24V ||  2.4W ||
|| apu1d4      || 12V || 12V || 12.0W ||


You want the Voltage to be as high as possible, causing your current to be as low. This in general makes transport over UTP wires more effient (higher voltage = less loss) and causes your adapters to work more effient (AC->DC adapters tend to be more effient and last longer if you keep the voltage as high as possible). 

We aim to get between 18V-20V to our node, Make sure to keep track of your input voltage [http://blog.fosketts.net/toolbox/power-ethernet-calculator/ Calculate] when using long cables.