This “ultrasonic” pest repellent just has circuit to control LEDs inside from r/assholedesign
This Adtala ultrasonic bug and rat repellent device is advertised as having an “Upgraded Smart Chip.” Reddit user SoggyMonsoon opened the case and found a circuit with 2 LEDS, 2 diodes, and three resistors, but no Upgraded Smart Chip. Does it even emit an ultrasonic tone? A commenter said: “this circuit WOULD emit ultrasonic sound. It looks like it would oscillate between the lights. Of course it would be extremely quiet since there is no amplification circuit here to the point that I highly doubt any living thing would be affected by it, but this circuit would in fact make 2 different pitches based on the light that was currently on / diodes in use. All electric circuits have a frequency. So along those lines any electronic device would be about as effective as this thing.”
Below, a video of a test with a Bell and Howell Ultrasonic Rodent Repeller. It didn’t work. In fact, rats seem to be attracted to it:
Image: Reddit