PURPOSE: To prevent the mis-detection of record size due to wow and flutter, by constituting the circuit with logic IC and converting the serial record size signal into parallel signal.
CONSTITUTION: When the photo electric conversion signal 302 is inputted and the level is changed at the time point a in Fig. from L to H, the switch 310-a is closed, and the counter 303 receives the turn control signal 301 and starts the count from the time point e. Further, the counter 304 starts count from the time point b. When the counter 303 counts the number of pulses N taking one revolution of the turntable as one period, it is self-reset and the signal of the output 306 of the counter 304 is at latch output. Simultaneously, the counter 304 is reset. Since the counter start time of the counters 304 and 303 has time difference by almost the pulse width of photo electric conversion pulse of the serial electric signal 302, the malfunction to the period variation of turntable is avoided.
ASADA AKIHIRO
IMAMURA OSAMU
