... And he's gone!

From the first day of using no new molehills more!
On a larger area it is advisable to use the two devices on two opposite corners.
Very important: It should be right next to it are no solid wall, because the totals are due to the resonance surface otherwise is very clearly audible. Otherwise, it has to be very quiet so you can still hear the occasional buzzing in 3m distance.
The durability of the device is about 2 years. Over this period occurs gradually moisture and brings the inner workings of the corrosion.
This part is actually not suitable with the lawn mower to go about it. They say it was surely a matter of course? Was not my wife.
After I bought the first pair in the retail sector, I was glad the same device recover from Amazon and will definitely buy new if their minds have abandoned.