1 OPAMP UA741
2 Resistor 1MΩ
1 Resistor 2k2
1 NPN Transistor 2N2222A
1 47n Capacitor

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C1 Ceramic Capacitor capacitance 10nF;
J1 Piezo Speaker;
R1 Rotary Potentiometer resistance 10kΩ;
R2 Resistor resistance 100Ω;
R3 Resistor resistance 470Ω;
R4 Resistor resistance 1kΩ;
U1 555 Timer package DIP8
VCC1 Battery & Connector voltage 9V