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本电路附加在具有选听复听功能的机器上。在选复听时实现自动停止。在这类机器上也往往有L E D电平指示器,多数指示器的指示状态不受音量电位器的控制。本文以常用的I C、L B 1405为例,它驱动5个L E D,其亮点数目随电平变化。选复听时,平均带速约为放音带速的10倍,其电平也提高数倍。因此,在选复听某个曲子时,5个L E D始终全亮,到空白区后(一般5s左右),L E D将全熄或只有第一个LED(LED_1)亮。而在一曲中的小信号或短时无信号区,因I C的脚
This circuit is attached to a machine with audible and audible functions. In the election to listen automatically when the stop. There is also a L E D level indicator on such machines, most of which are not under the control of the volume potentiometer. In this paper, the commonly used I C, L B 1405, for example, it drives five L E D, the number of bright spots with the level changes. Listen for the election, the average band speed is about 10 times the playback speed, its level is also increased several times. Therefore, when listening to a particular song, the five L E D are always bright, and after the blank area (typically about 5 seconds), L E D will turn off completely or only the first LED (LED_1) will light up. And in a small signal or short signal area, due to I C feet