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