HIGHLIGHT: --No Batteries NeededPre the button and the kinetic energy is converted into electrical energy. Don't worry about the battery running out of power--Distinguish front and rear doorsPre different buttons, and the receiver will emit different melodies. It is convenient to know which door has visitors coming--[Beautiful lights] Very eye-catching lights, very suitable for the elderly or deaf-mute-- [150 meters open distance] The actual use distance is suitable for most families-- [60 pieces of melody] rich melodies, giving the family a more beautiful environment--[5 levels of volume] You can choose the appropriate volume according to your family needs. High decibel volume can not mi visitors, low decibel volume will not disturb family rest--Free PairingThe button supports up to 8, and the receiver has no limit.--IP44 WaterproofIP44 supports life splashing water. If it needs to be placed outdoors, we recommend purchasing a profeional doorbell waterproof cover, which is safer and lasts longer--[Profeional after-sales guarantee] We have a complete after-sales team and have shot a lot of usage videos to better help customers. If there is a problem with the product, you can provide the video to us, we will help you Specification -- Receiver size: 95 x 65mm-- Button size: 74 x 40mm--Input voltage: AC110 ~ 240V, 50 / 60hz--Volume: 0-110DB--Melody: 60PCS Notice: 1. The distance is an open distance. In actual use, the distance will be shortened due to the increase of obstacles2. Although the frequency is 433MHZ, due to the incompatibility of the self-generating program, it cannot be used with other doorbells or other products.