{HEAD ~ The spectrum} is measured over {TAIL ~ a time period} of 1 to 1000 seconds, at intervals of 5 to 10 milliseconds or less 
is measured over
{ HEAD ~ The spectrum } is measured over { TAIL ~ a time period } of 1 to 1000 seconds , at intervals of 5 to 10 milliseconds or less
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH