(Partial Response Maximum Likelihood) A technique used to differentiate a valid signal from noise by measuring the rate of change at various intervals of the rising waveform. Bits generated by a modem or by reading a hard disk have uniform characteristics, whereas random noise does not. PRML uses digital signal processing (DSP) to reconstruct the data.On magnetic disks, PRML increases the number of bits that can be recorded over earlier methods. It uses an RLL encoding sequence of 0,4,4 and provides an 8:9 ratio of user data to recorded data. See RLL.