The filtered signal is envelope detected at a detector and the detected signal is compared with {HEAD ~ a predetermined squelch level} at {TAIL ~ a voltage comparator}  
The filtered signal is envelope detected at a detector and the detected signal is compared with { HEAD ~ a predetermined squelch level } at { TAIL ~ a voltage comparator }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH