This wireless doorbell consists of a receiver and a transmitter, just like traditional models. You plug the receiver directly into a free socket. The clever part is the transmitter: thanks to a piezo effect, pressing the doorbell button generates enough energy to send the wireless signal to the receiver, so no batteries are needed for the transmitter. You can choose from 25 different ringtones and melodies and also adjust the volume. Additionally, a blue LED flashes as soon as the doorbell is activated. The transmitter can be mounted either with the included adhesive pad or with the provided screws.