Bug Detector with Beep

Parts List:

R1 = 390 ohm, 5%
R2 = 390 ohm, 5%

C1 = 1000uF, 10V
C2 = 1.5uF, 10V
C3 = 3.9nF
C4 = 20pF, trimmer
C5 = 10nF (0.01uF or 103)

IC = 7413 or 74LS13 (2)

Please note: This circuit is not open for discussion. Although working perfectly, it was experimental. I will answer no emails in regards to this circuit.
If you are looking for a more serious and reliable bug detector, go to the Countersurveillance Monitor article on the Circuits Page.