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