The frequency of {HEAD ~ the back EMF signal} is determined from the zero crossings of {TAIL ~ the EMF signal} 
The frequency of { HEAD ~ the back EMF signal } is determined from the zero crossings of { TAIL ~ the EMF signal }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL