Voice controlled toy car circuit

Represents the principle circuit of a voice-controlled electric vehicle. When
a sound signal is emitted by speaking or striking, it is received by the stationary microphone BM and converted into a weak electrical signal
. It is coupled to the ① pin of the integrated circuit through the capacitor G.
The weak signal is converted by the internal amplifier of the integrated circuit. Amplified, and then output from @ pin, the amplified signal is coupled
to the input terminals ⑨ and ⑩ of the bistable circuit via capacitors C and C4. The output terminal Q of the bistable is connected to
the buffer driver to control the cut-off and conduction of the transistor VT. If the original output
terminal of the bistable circuit is low level, the transistor is cut off and the external relay K is released.
    When the sound sensor receives the sound, the bistable circuit flips to high level, the transistor
changes from cut-off to saturated conduction, the relay K is closed, and the controlled motor is powered on and
starts to work. When the sensor receives external sound again, Q becomes low level again, the transistor
is cut off, the relay K is released, and the controlled motor stops working. In the future, every time the microphone
receives a signal, the bistable circuit will flip once and the relay will act once.