{HEAD ~ The system} also serves as {TAIL ~ a testing system} for control umbilicals that usually are located near the pipelines 
serves as
{ HEAD ~ The system } also serves as { TAIL ~ a testing system } for control umbilicals that usually are located near the pipelines
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH