NH 1720 Aux Service Connection from 3PH

[GoneTractorN]

NH 1720 mfg in 1995

Please excuse any poor terminology as I'm not too tractor savvy.

NH parts catalog show option to add single remote from cylinder head on hydraulic lift housing where a plug currently is. Here is what the page heading looks like:1720 3 CYL COMPACT TRACTOR 20 SERIES (1/87-4/02) 05K02 ASC VALVE OPTION (K9) - NH-E. Also, I have tried to attach an image(I'm new to Tractor By Net).

I'm wondering how this works?

Is the line under constant pressure?

Can it be used to power a hydraulic top link?
If so, where can the return go near the back of the tractor?

Thanks for any help.