What is a power box?
The crystal has 2 hyd tappings on the back. If you are using a tipping trailer for example, you would use only one, operated by the small lever on the quadrant, in the rearward direction. if you had something that required double action, for example, a log splitter, then you would use both tappings and the lever would work both by moving it all the way foreward or all the way back.
If you want constant pumping then complete a hyd circuit using both tappings and fix the lever so that it's in the rearward position.
The only thing about this is that if you have a machine, for example, a hydraulically powered bale wrapper, that is constantly running hard then you should pipe the return pipe directly into the gearbox, to minimise the back pressure and friction in the oil which causes it to heat up.
