Feature: 1. Wide Application: Two doorbell transmitters and two receivers, widely used in homes, apartments, offices, schools, hospitals, , etc. 2. Self Generating: When the finger presses the doorbell, the kinetic energy is converted into electrical energy, and there is no need to change the battery for the doorbell. 3. Strong Signal Penetration: Using 433.92MHz wireless signal, it can penetrate 3‑4 doors, and the receiving distance in open areas can reach 150 meters. 4. Adjustable Melodies and Volume: 38 ringtones can be switched freely, 3 levels volume can be adjusted, and silent mode can also be set to meet the needs of different scenarios. 5. Multipurpose: Not only a doorbell, but also a siren, suitable for elderly people, babies, pregnant women and patients who sleep alone to deal with emergencies. 6. Easy Installation: IP44 waterproof level, it is not afraid of wind and rain even outdoors. Complimentary double sided tape, no wiring and no damage to the wall; it can also be installed with screws. Specification: Item Type: Wireless doorbell Material: ABS Operating Frequency: 433.92MHz Standby Power Consumption: 0.25W Music: 38 Volume: 3 levels and mute Controllable Volume: ≥50dB/1m Receiving Distance: ≥150 meters (unobstructed in open space) Receiver Working Temperature: -10℃-+45℃ Transmitter Operating Temperature: -20℃-+60℃ Receiver Size: 78 x 54 x 20mm/ 3.07 x 2.13 x 0.79in Transmitter Size: 66 x 40 x 20mm/ 2.6 x 1.58 x 0.79in The transmitter does not need a battery, it is self generated by pressing. Package List: 2 x Doorbell2 x Receiver2 x Sticker Note: 1. The remote control distance is affected by the use environment, and the distance will vary due to different use environments.2. When using wireless electronic products, you should avoid strong interference sources such as metal covers, large electronic equipment, and electromagnetic fields, so as to avoid the remote control and receiver from not working properly.3. Do not use this electronic product abnormally. Abnormal use will reduce the performance and life of the product. In severe cases, it will damage the product and bring dangers to your safety.