Installation Steps:   
Step 1:Install Metal Film Resistor R1=200K;R2=2K;R3=470ohm.   
Step 2: Install Capacitor:C1,C4=104pF;C2,C3=222pF;C5=100uF.   
Step 3:Install 2pcs S9012 on Q2,Q3;1pcs S9018 on Q1;1pcs potentiometer on VR1.   
Step 4:Install the LED with the long leg as the positive pole, corresponding to the square pad mounted on the board.   
Step 5:Install Buzzer and Power socket.   

Note:   
The installation of electronic modules requires basic knowledge and requires a certain electronic professional foundation and hands-on ability. Please purchase carefully!   
Manual measurement, with small error. Please check size in detail before purchase.   
Real colors may slightly differ from the pictures, as it depends on specific monitor settings and light brightness.