How does Ultrasonic Technology work? The Electronic Ultrasonic Pestcontro II Deluxe emits set sounds determined by settings on the unit. This allows the device to target different pests, such as mice and rats. Pests do not like this constantly changing environment, which causes them to leave the area. The Pest Contro Deluxe utilitizes "Sweep Sound Technology (SST)", a Lentek feature that creates a fluctuating ultrasonic sound to target pests within the ranges. This creates a constantly changing environment to pests that is difficult to ignore. Will it affect appliances or Pets? No. It will not affect computers or appliances. The Pest Contro Deluxe generates ultrasonic sound waves which are above the hearing of humans, dogs, cats fish and birds. these ultrasonic frequencies CAN be heard by rodent pets such as hamsters, gerbils, and rabbits. However, by positioning the unit in an area away from rodent pets, you will not cause it discomfort. How many will I need This device can provide coverage for a large size home. Larger homes or multiple floor homes and structures will need multiple units throughout for adequate effectiveness. Since each home is different, place the device in the area with the most problems and monitor the results. Features audible test button night light three LED status indicators UL and CE approved EPA Registered 72092-CNN-001 Two year warranty Size: 4 1/4"Hx 71/2"Lx 31/4"W. Weight: 6.8 oz.