Logic control circuitry 320 is connected to {HEAD ~ the first tracking bit line} and usable to convert the voltage change on {TAIL ~ the first tracking bit line DBL} into the SAE signal 
Logic control circuitry 320 is connected to { HEAD ~ the first tracking bit line } and usable to convert the voltage change on { TAIL ~ the first tracking bit line DBL } into the SAE signal
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH