{HEAD ~ The signal variations} provide {TAIL ~ step count signals}, and the step count signals are compared to the command pulses to detect a disparity 
provide
{ HEAD ~ The signal variations } provide { TAIL ~ step count signals } , and the step count signals are compared to the command pulses to detect a disparity
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH