| 摘要 |
PURPOSE: To fix the issue level of an alarm regardlessly of the increase/decrease of a mark rate by inputting a voltage correlated to the mark rate to a compara tor circuit for transmitting an alarm signal as a threshold value. CONSTITUTION: The voltage of the peak value correlation of a timing component is inputted from a peak detection circuit 16 to a comparator circuit 18 as a peak detecting signal P. Besides, the voltage of mark rate correlation is inputted from a mark rate detection circuit 17 to the circuit 18 as a mark rate detecting signal M. At the circuit 18, this mark rate detecting signal M is defined as the threshold value and compared with the peak detecting signal P. When the peak detecting signal P is lower than the threshold value M, an alarm signal A is transmitted to the outside, a reset signal R is transmitted to an identification reproducing part 13 and a timing extraction part 14 at a reproduction repeater 10, and a data signal D and a clock signal C are reset. Therefore, a threshold voltage is controlled corresponding to the change of the mark rate and the issue level of the alarm is fixed regardlessly of the change in the mark rate. |
