This doorbell extender works by listening for your existing doorbell to ring. When it does, the transmitter sends a wireless radio signal up to 100 feet to the plug-in door chime receiver. The unit is simple to install. Simply place the extender's transmitter on top of your existing chime and then plug the receiver into a standard wall outlet. White cover and extenderHear your doorbell throughout your homeExtender activates additional chime when your doorbell ringsChime plugs into any standard wall socketTransmission range up to 100 feetAdjustable volume control