Directional "CRA" for ternary digital recording

A directional Controlled Return-to-AC (CRA) code is conceived where a "break" is substituted for a conventional step "transition" in saturated digital recording. The "breaks" are embedded in frequency controllable rapid dithering pulses. Each break, with a pre-determined break width, has directional freedom during the encoding WRITE mode. The combination of direction and its presence or absence allows the mapping of three binary bits into two CRA digits. A 50 percent information density increase over the popular MFM code is potentially realizable. The read signal from the CRA code has a well confined signal spectrum and requires neither dc nor low frequency spectral components. It is self-clocking and has effective overwrite. Since the readback waveform contains only directional "doublets", its amplitude is stable and its timing is accurate. These characteristics allow very simple and reliable data detection. "CRA" is believed to be one of the first practical realizations of a free-directionality code in saturated digital magnetic recording.