These mouse repellers emit ultra sonic sound waves that attack the auditory and nervous system of household pests causing them to avoid the area the repeller is situated inr r easy to use the device simply plugs in and has an effective range of 30 sqm a night light is operated by a switch on the side that also leaves the repeller emitting ultra sonic wavesr r plug in pest repellerr night light featurer 30 sqm ranger set of 4