| 摘要 |
<p>PROBLEM TO BE SOLVED: To stably detect the header even when an error is generated to some extent in discriminating a duty of a reproducing control signal. SOLUTION: The duty of the reproducing control signal shaped in waveform by a waveform shaping circuit 1 is discriminated by a duty discriminating circuit 2, arc its result is held by a shift register 3. A value of an analog voltage obtained by converting the sum of values of outputs Q2-Q10 of the shift register 3 by a D/A converter 7 is compared with a reference voltage E1 by a comparator 8, and when the value of Q2-Q10 is 1 as >=8 bits, 1 is outputted as a result of comparison. In order to obtain an AND condition of an output value of an NOR circuit 5 for taking NOR of output values of Q1 and Q11 of the shift register 3 and an output value of the comparator 8 by an AND circuit 6, even when the most significant bit and the least significant bit are both 0 as a result of the duty discrimination, and an error is generated between them to some extent to be 1 as >=8 bits, 1 is outputted from the AND circuit 6 to enable the VASS code header to be detected, and a header signal is outputted from a D-type flip-flop 9.</p> |
