| 摘要 |
PURPOSE:To stop the delivery of noise signal which is harmful, by the amplification and output of normal input signal to the preset level manually and interrupting the output when the input signal is absent. CONSTITUTION:When the input signal is present at the input terminal 1, the signal is amplified at the AGC amplifying circuit 2, it is attenuated by the specified amount at the attenuation circuit 4, and output from the output terminal 5 in a suitable level. Next, no input signal is present to the input terminal 1, the signal appeared at the pickup terminal 3a of the detecting section 3 is also absent. Thus, the transistor Q1 in the setting release circuit 7 is OFF. Then, even if the slider 6a of the attenuation setter 6 is set at any position, the control voltage fed from the setter 6 to the attenuation circuit 4 is zero. Thus, even if noise is input, it is interrupted at the attenuation circuit 4 and not delivered from the output terminal 5. |
