Vertical movement of the plunger actuates a cam or {HEAD ~ screw} to vary {TAIL ~ the setting} of the control element of the level control system 
to vary
Vertical movement of the plunger actuates a cam or { HEAD ~ screw } to vary { TAIL ~ the setting } of the control element of the level control system
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH