Unfortunately, probably one of the two devices was defective from the outset. Also sunlight could coax him to this day no sound. The other seems to perform his duties. Within a few yards of the equipment I have today approximately 4 weeks may find no further Wühlmausaktivitäten (. The range could be better. But at this price you can buy more than one device Yes. You should only not defective. As Annoying ! Therefore, there is only one star from me.