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