Feature: 1. 2 Doorbell and 1 Receiver: Can be used for the front and rear doors, sound at the touch of a button, and you can set separate corresponding ringtone. 2. Self Powered Door Bell: Ding dong doorbell adopts self generating design, built in kinetic energy power generation, no need to worry about batteries. 3. Long Range: Self generating doorbell is engineered for wireless super penetration, the signal can penetrate 3‑4 walls, and can reach up to 200m in open area. 4. Loud Volume: There are 38 songs can be changed at will, and the sound quality is rich and pleasant, including classic doorbell tones and music ringtones. 5. Wide Usages: The waterproof door bell can be used in homes, villas, hotels, factories, and can also be used for one key calls for the elderly, patients and pregnant women. Specification: Item Type: Self Powered Doorbell Material: ABS Uses: Homes, villas, hotels, factories, the elderly, patients, pregnant women for one key call Type: 2 Transmitter and 1 Receiver Doorbell: Power Supply: Self Generated Open Space Transmission Distance: Approx. 200m/219yd Indoor Transmission Distance: Approx. 50m/55yd RF Frequency: 433MHz Receiver: Power Supply: AC110-240V Ringtones: 38 (4 levels volume adjustable) Ringtone Volume: ≥50dB at 1m distance. Package List: 2 x Doorbell1 x Receiver2 x Sticker Note: Please supply power according to the voltage used, using other voltages may cause fire and product damage!