The doorbell receiver is powered by batteries and does not require occupying a power outlet. The receiver has 3 LEDs that flash when the buzzer sounds. There are 36 ringtones, 4 volume levels, which can be muted. 150m transmission distance, IP44 waterproof level. Easy installation, just attach the transmitter to the door frame with double-sided tape or screws. Installing the transmitter 1. Installation of 23A12V battery included. 2. Fixing to the door frame using double-sided tape or screws. 3. Any metal interferes with the signal and reduces the transmission distance. Please install the transmitter away from metal. Specifications Volume: 25-85dB Doorbell: 36 songs Sealing: IP44 Transmission distance: 150m Transmitter battery: 123A 12V (included, can be used for more than 15 months) Receiver battery: 3AA (not included)