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