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