Advanced transmitter: Operating temperature between -10C and 45C. This doorbell can withstand strong winds and heavy rain. Long Wireless Range: 300m long transmission distance can cover the entire house without disturbing other devices. 45 beautiful melodies: Choose from a rich selection of 45 melodic ringtones. Volume adjustable in 4 levels, the maximum volume is 110 dB, so that the elderly and hard of hearing people can also hear. Memory Function: This doorbell will remember the saved volume and ringtone settings. So in the event of a power outage, once power is restored, the doorbell will automatically restore the last saved settings. EASY TO INSTALL: The doorbell can be easily and quickly attached to the wall using dowels and screws or the adhesive sheet provided. This doorbell system can be expanded with 2 additional transmitters and multiple receivers for increased coverage.