Latest Push-Rf Technology & Battery-Free This Wireless Doorbell Is Self-Sufficient, Does Not Require Cables or Batteries, Protects The Environment and Saves Your Money. When The Transmitter Is Pressed, It Generates Electricity By Itself and Sends A Stable Signal to The Receiver. Never Again Worry About Damaging The Wall or The Doorbell When Changing The Battery 38 Ring tones and 4 Volume Levels Our Wireless Stereo Loudspeaker For Heilwiy The Doorbell Delivers A Rich and Clear Sound. It offers A Wide Selection of 38 Ring tones and 4 Volume Levels (Including Muting) to Suit Your Personal Taste. Press and Hold The Volume Button to Return to The First Ring (Dingdong). with A Memory Function, The Radio Bell Remembers Your Last Settings After A Power Failure. No Crosstalk & False Alarms This Cordless Doorbell Has Strong Penetration and Anti-Interference. The Area For Heilwiy Multiple Obstacles Is Up to 152 M (500 Feet) and In Open Areas It Is Up to 305 M (1000 Feet). It Doesn'T Interfere with Other Equipment In Your Home or Those of Your Neighbors, and Ensures That You Never Miss A Visitor, Even If You Are A Few Rooms Away or On A Different Floor. Quality Assurance and Satisfied Service Our Cordless Trgong Is Dustproof and Ip44 Waterproof and Can withstand Various Harsh Weather Conditions. According to Our Test, The Push Button Can Achieve A Maximum Service Life of 20 Years and Up to 150,000 Clicks. We Also offer A 2 Year Guarantee Plus 60 Days Satisfaction or Right of Return. If You Have Any Problems with Our Products, Please Feel Free to Contact Us For Heilwiy A Satisfactory Solution.