Instruct: Classify a given Amazon review into positive or negative sentiment.
Query: Failure

Another failure. I bought a B&D; unit and that did not work. I was really hoping that this one would. It comes as a nice unit that you simply plug into the wall socket. It has flashing lights and a test button to confirn that it is working because otherwise there is no sound.The first failure was in a room adjacent to the main basement where I had plug in the unit. This was one week after installing. I thought that the ultrasonic waves could not penetrate walls but then it failed again with rat trapped in the main basement-20 feet from the unit. So be forewarned that this device does not work for everyone.