This handy device emits electromagnetic and ultrasonic waves to scare rodents away from food sources simple to use it simply plugs in a switches on with an activation light to signal when it is in operationr r not audible to humans or house hold pets this repeller will help humanely clear nuisance pests without the use of harmful chemicals the electromagnetic waves affect the nervous system while the ultrasonic waves are like a siren in the pests earsr r multi functionr plug in and easy