| 摘要 |
PURPOSE:To alarm the abnormality of an output frequency by detecting a direct current voltage level equivalent to the control input of a voltage controlled oscillator, and rising an alarm when the size, in which the direct current voltage level is changed accompanying the reference frequency, exceeds a prescribed range. CONSTITUTION:When switching to a switching circuit 3 in accordance with the control of a control circuit 10, the control input voltage of a voltage controlled oscillator 4 is changed. The variation appears at the output of a potential difference detecting circuit 8 and a comparing circuit 9 decides whether or not the variation is prescribed range. When the variation is in the prescribed range set beforehand, an action is normal, and when the variation is smaller or larger than the range set beforehand, it is considered that the abnormality is present at the output frequency and an alarm output is generated. Thus, with a simple circuit, it can be detected that the abnormality occurs at the output frequency. |
