Electronic Safecracking

Ever seen a safecracker at work on a television detective or police program? We don't want you taking up a life of crime, so try your safecracking skills on this Project.

Real safecrackers carefully move the safe's dial until they find the right combination which will unlock the safe. In this Project you turn the Control Knob until you find the position that makes the sound produced by the circuit go away.

Real safecrackers also often use a stethoscope (like doctors use) to help them hear the movements of the safe's dial. In this Project you'll use the Earphone to hear when you've finally "broken the safe!"

Connect the Earphone, turn the power ON, and press down on the Key. You'll hear a sound through the Earphone.

Now carefully readjust the Control Knob. Press the Key again, and you'll notice the sound Is either louder or quieter. Again re-adjust the Control Knob and press the Key again. Keep doing this until you find the Control Knob setting where the sound disappears altogether or is faintest. When you find this point, congratulations, you've broken the safe!

This game can get too easy when you use your eyes all the time. Try it blindfolded, and let a friend just briefly press the Key for you each time. This is another audio oscillator circuit, like our Earsplitier in Oscillator Section. Compare the two projects. What do you think causes two audio oscillators to make different sounds?

Make a note of your guess, later we'll see how we can change the sound of an audio oscillator ...