Spectrum analysis can be used to create a profile of an active signal source that can be analyzed to identify the type of {HEAD ~ source} producing {TAIL ~ the signal} 
Spectrum analysis can be used to create a profile of an active signal source that can be analyzed to identify the type of { HEAD ~ source } producing { TAIL ~ the signal }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL