When printing, the surface potential of {HEAD ~ the printing medium} directly below {TAIL ~ the printing head} is acquired 
directly below
When printing , the surface potential of { HEAD ~ the printing medium } directly below { TAIL ~ the printing head } is acquired
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH