Low frequency oscillation circuit

Gate circuits
F4, F5, and F6 together form a low-frequency
oscillator to drive ultra-high-brightness light-emitting diodes
to flash. The light-emitting diodes can be arranged around
the booth to play a decorative role.
    (4) How to use the product automatic introduction
machine must be pre-recorded before use. When recording,
press and hold K2i and the speaker will emit two beeps, and then you can record into the microphone. After recording the product introduction voice,
release S2. The speaker will beep again to indicate the end of the recording. If the recording time exceeds the time allowed by the chip, a
"beep, beep" will be emitted when the chip's allowed time is reached. "Two beeps will force the recording to end. S1 is the stop button. When the product introduction machine uses
voice introduction, just press Sl to stop the voice introduction.