(PRML) A method for converting the weak
analog
signal from the head of a
magnetic disk drive into a digital
signal. PRML attempts to correctly interpret even small
changes in the analog signal, whereas peak detection relies
on fixed thresholds. Because PRML can correctly decode a
weaker signal it allows higher density recording.
For example, PRML would read the magnetic flux density pattern
70, 60, 55, 60, 70 as binary "101", and the same for 45, 40,
30, 40, 45. A peak detector would decode everything above,
say, 50 as high, and below 50 as low, so the first pattern
would read "111" and the second as "000".