Quantity   Component name
2 × 500K ohm potentiometer Variable resistor
1 × 1K ohm resistor
1 × 4,7K ohm resistor For the lowpass filter near the output
1 × 200 ohm resistor
2 × 555 timer One 556 timer also does the job
1 × 10uF electrolytic capacitor For the lowpass filter near the output
2 × 0.1uF capacitor
1 × red LED
1 × push button
1 × mini-jack connector
1 × 9v battery
1 × old alarm proximity sensor case (optional : D)