Item carrying reminder circuit (1)

Circuit working principle: The circuit on the left side of the dotted line is drawn to facilitate the explanation of the principle.
The original door-controlled automatic lighting circuit of the car. IC 1 is a commonly used integrated circuit voltage stabilizing block, which
provides 5v working voltage for the voice generation circuit. R3 is the external oscillation resistor of IC2 .
IC2, IC 3 and peripheral resistors R4, R5 and capacitors C1 to C5 form a voice amplification circuit .