3 of 4 devices defective - keien effect

I had four units ordered after it found a mole useful our garden "creatively reshape". Of the four devices made any sounds when you press the check button. But in actual use then worked only one device but with a loud beep sound every few seconds, so you do not amazingly popular with the neighbors (I actually thought the part would work with ultrasound).
Effect (the only functioning part): absolute zero.

Incidentally, I have pretty much used every means that allegedly against moles helps: It did not help. One must simply wait until the cattle moves on.