The peaks of {HEAD ~ the forward and rear output pulses} are converted into {TAIL ~ DC voltage levels}, which are then fed into a comparator circuit 
The peaks of { HEAD ~ the forward and rear output pulses } are converted into { TAIL ~ DC voltage levels } , which are then fed into a comparator circuit
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH