Electronic watchdog circuit

It is composed of Doppler effect sensor Nl (RD627), operational amplifier N2 (LM358), dog barking imitation sound-specific
integrated circuit N3 (KD5608), etc.
    When no one is active in the Nl "monitoring" area, Nl's ⑥ pin has no signal output, N2's ① pin output is low potential , VT is cut off, and N3
's ② pin is low potential and does not work. When someone moves in the "monitoring" area of ​​N1, its ⑥ pin outputs a low-frequency signal. This signal is amplified by N2
and turns on VT. Therefore, N3's ② pin gets a positive trigger signal and makes a dog barking sound. This sound prompts people who are active in the Nl "Linshi" area
to leave the area and at the same time alert the owner. Adjust RP. The "monitoring" distance of Nl can be changed.