JPS57183645A - Dropout counter of discoid information recording medium - Google Patents

Abstract

PURPOSE:To facilitate an easy and accurate inspection for the number of dropout groups as compared with a visual inspection using a microscope, by producing position pulses with the occurrence of a dropout and carrying out counting. CONSTITUTION:A dropout pulse (a) sets an FF4, and a counter 5 counts 1a clocks CL with the output of the FF4 to deliver an end signal when a prescribed counting is over. As a result, a monostable multivibrator 7 is triggered to deliver a rotary position pulse (d) of a prescribed duration. The pulse (d) is supplied to an FF8 and a monostable multivibrator 9. When the pulse (a) arrives again in a period of H level of the pulse (d), a signal (e) is delivered from the FF8. When the dropout does not exist at a moment when a disk has three turns from the first dropout, a dropout end pulse (f) is extracted out of a monostable multivibrator with the fall of the signal (e). As a result, an inspector confirms the existence of the dropout group. A counter 10 counts the number of continuous tracks of the dropout.