First of all, the Katzenschreck was supplied by Amazon within a day. After the 9V Blckbatterie was used, the Katzenschreck began its work in my garden since January. And I have to say very successful. To date, no cat has "immortalized" in my garden.
The device funktioniet with ultrasound, which is not audible to at least adults. For the functional test you can do these sound waves audible. So the switch to the correct setting. As my son and some of his friends hear the sound waves even when "toneless" setting, we put the cat fright over the easy-to-use on-off Schlater when he is in the garden. After the Katzenschreck starts work again.
Conclusion: I am very pleased with my Katzenschreck - the effect of the ultrasonic waves keeps me the pests from the garden. The device is easy to use and can be mounted as desired and firmly. I can only recommend the device!
UPDATE: the Katzenschreck is only for about a year in operation. The first battery is still doing its job and the cats like my garden no more than toilet. I am a satisfied Katzererschrecker!