实验箱上的蜂鸣器发出对应的音调（中音），当同时按下L和1

代码说明：

实验箱上的蜂鸣器发出对应的音调（中音），当同时按下L和1-7时是，蜂鸣器发出低音，同时按下H和1-7时，蜂鸣器发高音。只要按键没松开，蜂鸣器一直发声，直到松到按键。-The buzzer sounded on the test box corresponding to tone (Tenor), when at the same time when you press the L and 1-7, the buzzer sounded a bass, while pressing the H, and 1-7 when the buzzer made treble. As long as no release button, buzzer sound has always been, until the pine to the button.