Two electrical cables of an articulated robot arm are in the form of {HEAD ~ helical cords} which lengthen and shorten respectively during {TAIL ~ the rotation} of the arm 
lengthen during
Two electrical cables of an articulated robot arm are in the form of { HEAD ~ helical cords } which lengthen and shorten respectively during { TAIL ~ the rotation } of the arm
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH