| 摘要 |
PURPOSE:To eliminate the noise due to spectrum spread, etc., generated for switching of a frequency or an amplitude by providing a circuit which detects the change of the frequency or the amplitude of an input signal and releasing lock state of an automatic level control circuit when this change is detected and sufficiently attenuating the level of an outputted signal and returning it to the original state again thereafter. CONSTITUTION:The AC signal outputted from a variable frequency oscillator 18 is attenuated by a variable attenuator 29 and is amplified by an amplifier 30 and is outputted from a terminal 38. The output signal of a phase comparator 19 constituting a phase synchronizing circuit is supplied to a transient detector 21 also. When the frequency or the amplitude of the AC signal outputted from the terminal 38 is changed, the transient detector 21 momently opens a switch 35. A switch 36 is closed to increase the extent of attenuation of the variable attenuator 29, and the level of the signal outputted from the terminal 38 is sufficiently attenuated. Consequently, malfunction does not occur in a measurer or the like connected to the succeeding stage of a transient level suppressing circuit even if the signal is switched, and switching is quickly performed. |
