A Logical Reading System for Nonreturn-to-Zero Magnetic Recording

The nonreturn-to-zero method for the magnetic recording of binary information saturates the surface in a continuous fashion, one sense of saturation being used for a ``1'' and the opposite sense of saturation for a ``O.'' A system is described for reading NRZ digital data which utilizes the inherent alternating characteristic of the readback signal waveform to effect a logical correction. The reading system corrects the ``normal'' sources of error which limit the usable bit storage density and set the degree of reliability. The system employs only amplitude sensitive waveform operators and samples the readback signal only at the regular clock times.