| 摘要 |
PURPOSE:To decode and reproduce bit data surely irrespective of the change of carrying speed of a card and the change of density of data recording by setting timing of reading gate signals basing on a clock pulse period. CONSTITUTION:A magnetic head 1 reads a clock pulse written in the initial area on a card 2, and an initial clock counter 7 counts clock pulses from a binarizing circuit 5 and sends a count up signal to a controlling circuit 6. The controlling circuit 6 sets a permission signal to H at rising of the next clock pulse, and further sets to L at next rising. A clock period counter 9 counts oscillation clocks from an oscillator 8 while the permission signal is H, and holds the count value as clock period T during reading output. A reading gate signal generating circuit 10 outputs a pulse train of period T, duty ratio 50% delaying from timing of arrival of clock pulse by phase T/4, and sends the result to the controlling circuit 6 as a reading gate signal.
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