| 摘要 |
PURPOSE:To extremely simplify the circuit constitution for discriminating a pulse interval by setting a time ratio of the pulse interval to 5X2<n>:7X2<n>:9X2<n> ((n) is a natural number) at the time of executing the MFM modulation. CONSTITUTION:A time ratio of three kinds of pulse intervals T1, T2 and T3 of an MFM modulating signal is set so as to come to 5X2<3>:7X2<3>:9X2<3>. When an optical signal is made incident on a photodiode 16 of a fixed terminal 5, a reference clock pulse CK from a clock oscillating circuit 19 is counted between pulses of a light receiving signal SR by a binary counter 20. Its count value comes to a count value corresponding to one of the pulse intervals T1, T2 and T3. The pulse interval of the received MFM signal generates an error with respect to the transmitted pulse interval, but by monitoring only the upper three bits, the pulse interval fluctuation of about 10% even at the smallest is allowable, therefore, a sufficient performance for practical use is obtained. |
