Digital recording circuit for a magnetic card, especially for toll-road ticket

摘要

This circuit comprises a coding circuit which codes the input data (400) via a modified frequency-modulation (MFM) system and outputs, to a recording amplifier, a string of codes (408) modulated by modified frequency modulation (MFM), beginning with at least four "0" data bits which follow one another, thus reversing the magnetisation at the boundaries of the bit cells.