Feature: 1. Self Generating: The transmitter has a built in power generation module, no batteries, no wiring, beautiful and easy to put in place. No need to worry about the battery. 2. Super Signal: The wireless signal of this doorbell has strong penetrating power, the signal can penetrate 3 or 4 walls and up to 150 meters in the open area. 3. Music Bell: This doorbell has loud volume. The sound quality is thick and dynamic. There are 38 musics for you, including the classic doorbell sound and music ringtones. 4. Waterproof: This wireless doorbell with waterproof design, even if it is raining, it does not affect the use. It can be installed in the outdoor. 5. Widely Used: This doorbell can be used in homes, villas, hotels, factories, office buildings, etc. It can also be used for the elderly, patients and pregnant women to call with one key. Specification: Item Type: Wireless Doorbell Material: ABS Weight: Approx. 120g/4.23oz Application: For families, villas, hotels, factories, for the elderly, the sick, pregnant women one key call Doorbell Parameters Power Supply: Self Generating Transmission Distance: Unobstructed ≥150m RF Frequency: 433MHz Receiver Parameters Ringing Tone: 38 Songs (4 Adjustable Levels) Ringing Volume: ≥ 50DB / at 1m . Package List: 1 x Doorbell1 x Receiver1 x Sticker1 x Instruction Note: Please supply power according to the voltage in use, use other voltages may cause fire and product damage!