Advanced transmitter: Operating temperature between -10 °C and 45 °C. This doorbell can withstand strong wind and heavy rain. Large wireless range: With a transmission range of 300 m, the entire house can be covered without disturbing other devices. 45 beautiful melodies: Choose from a wide selection of 45 melodic ringtones. Volume adjustable in 4 levels, the maximum volume is 110 dB, so that even the elderly and hard of hearing people can hear. Memory function: This doorbell remembers the saved volume and ringtone settings. In the event of a power failure, the doorbell automatically restores the last saved settings after the power is restored. EASY TO INSTALL: The doorbell can be easily and quickly attached to the wall with dowels and screws or the adhesive film provided. This doorbell system can be expanded with two additional transmitters and multiple receivers to increase the range.