User manual

27
Tones and frequencies
The sound starts at 1.5 kHz and ends at around 40 kHz.
A young person hears notes up to about 20 kHz; in old age,
however, the limit can be well below 10 kHz. But you will only
be seriously hard of hearing when notes of 3 kHz can no longer
be heard. The last note of 40 kHz should not be perceivable by
humans. For dogs and cats, the sound can be very uncomfort-
able. You can also use the highest note to test a bat detector,
because the calls of bats are also in this range.
14 Safe-deposit cracker
This electronic lock has only two buttons, but only the rightful
owner (in this case the Queen of England) knows how to
operate them. Here, you become a safecracker and find out
the secret code. The corresponding program is started with a
resistance of 470k Ω (yellow, violet, yellow), which was previ-
ously used for the lie detector.