| 摘要 |
PURPOSE:To prevent malfunction owing to a current amplification factor of an APD, the temperature characteristic of bias voltage or shot noise, by monitoring a identification reproduction pulse by an alarm circuit to detect a pulse error and outputting an alarm. CONSTITUTION:A pulse 5 having a fixed width is produced from a identification reproduction circuit 3 consisting of a mono-multi of an alarm circuit. Then a pulse error is produced by the noise of an APD. In such a case, a new pulse is produced between pulses of a signal or a reproduction pulse is outputted with its width changed. The pulse 5 is supplied to one side of an AND circuit 8 together with an output delayed by a delay circuit 6 applied to the other side of the circuit 8. A monostable multivibrator 10 is triggered by the output 9 of the circuit 8, and an alarm output 11 is outputted from the vibrator 10. This prevents malfunctions owing to a current amplification factor of the APD, the temperature characteristics of bias voltage or the shot noise. |
