a conversion section configured to convert {TAIL ~ the equalized waveform} into {HEAD ~ a maximum likelihood sequence} by carrying out metric calculation based on average values of the equalized waveform in vicinities of a positive signal level, a negative signal level and a zero signal level 
a conversion section configured to convert { TAIL ~ the equalized waveform } into { HEAD ~ a maximum likelihood sequence } by carrying out metric calculation based on average values of the equalized waveform in vicinities of a positive signal level , a negative signal level and a zero signal level
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH