a first pressure regulator in communication with {HEAD ~ said first reservoir} for controlling {TAIL ~ pressure} supplied through said pressure supply conduit to said first reservoir; and 
for controlling
a first pressure regulator in communication with { HEAD ~ said first reservoir } for controlling { TAIL ~ pressure } supplied through said pressure supply conduit to said first reservoir ; and
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH