The current is automatically reversed at {HEAD ~ the point} of {TAIL ~ zero motion} of the reciprocating mechanism during each rebound 
of
The current is automatically reversed at { HEAD ~ the point } of { TAIL ~ zero motion } of the reciprocating mechanism during each rebound
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH