When {HEAD ~ a fluid pressure} in {TAIL ~ the extension chamber} exceeds a certain level, the plug disengages the valve seat such that fluid may flow from the extension chamber, in the entry port, along the relief passageway, and out the exit port 
When { HEAD ~ a fluid pressure } in { TAIL ~ the extension chamber } exceeds a certain level , the plug disengages the valve seat such that fluid may flow from the extension chamber , in the entry port , along the relief passageway , and out the exit port
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH