Can't hear the calls of bats? With the right technical tools, you can – and that's not all. Build your own high-quality ultrasonic detector and experience it for yourself! This kit makes it an easy and foolproof exercise: the circuit board is already populated with numerous SMD components. You only need to solder a few parts yourself and wire the board with a microphone, speaker, and adjustment controls. Modern integrated circuits ensure high sensitivity and volume. Then you can embark on an exploration: with the finished detector, you can make the ultrasonic calls of bats audible. This way, you can track these fascinating flying artists in the dark, even where they usually go unnoticed while hunting for insects. But it's not just bats; many technical devices also emit ultrasound. You will be surprised by how many inaudible sound sources surround us. Give your ears superpowers: 20 kHz is not enough!.