| 摘要 |
PURPOSE:To produce an alarm assuredly even with the artificial synchronization by providing a detecting part which detects that no input signal appears in a cycle of a reference signal and no reference signal appears in a cycle of the input signal. CONSTITUTION:A step-out detector 40 consists of detecting parts 41 and 42, and the part 41 detects that no input signal IN appears in a cycle of a reference signal given from a phase synchronism detecting circuit 10. While the part 42 detects that no reference signal appears in a cycle of the signal IN. Differentiators 43 and 44 are provided at the preceding stages of parts 41 and 42 together with timing detectors 45 and 46 set at the next stages of the parts 41 and 42 respectively. In such a constitution, the outputs of detectors 45 and 46 are set at 0 in case the signal IN and the reference signal appear alternately. Then the outputs of detectors 45 and 46 are set at 1 in case the signal IN has a 1/N frequency compared with the reference signal. Then an alarm ALM is delivered through an OR gate 51. The output of the detector 46 is set at 1 when the signal IN has a frequency N times as much as that of the reference signal. Then an ALM is delivered through the gate 51. |
