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