Depending on the nature of the signals of interest, the signals detected may be reflected signals generated in response to a carrier signal produced by the communication device, or {HEAD ~ active signals} produced by {TAIL ~ active sources} 
produced by
Depending on the nature of the signals of interest , the signals detected may be reflected signals generated in response to a carrier signal produced by the communication device , or { HEAD ~ active signals } produced by { TAIL ~ active sources }
OTH OTH OTH OTH OTH OTH OTH OTH 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 HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL