| 摘要 |
PURPOSE:To improve the operating performance in the active mode of a recorder, by providing an undesired signal selecting and amplifying means, detecting the undesired signal through the rectification and the shaping of waveform and controlling the working of an undesired signal eliminating filter. CONSTITUTION:An undesired signal selecting means 1 consists of a filter 11 and an amplifier 12. An undesired signal rectifying and shaping means 2 consists of a rectifying circuit 21, a limiter circuit 22 and a time constant circuit 23. An undesired signal detecting means 3 detects the undesired signal with the output of the means 2 and comprises a comparator. The level setting e0 of the means 3 is done in correspondence to the undesired signal elimination factor which is required for a noise reducing circuit (NR) device. Thus the presence or absence of the undesired signal is detected automatically, and at the same time the malfunction due to the instantaneous high band signal caused by the musical component can be avoided by the circuit 23. A control means 4 is turned on and off by the output of the means 3 to automatically control the working of an undesired signal eliminating filter 5. In such way, the operating performance can be improved when the recorder is active. |
