Features: 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_x000D_ Material: ABS_x000D_ Working Voltage: AC 100V-230V 50/60Hz_x000D_ Operating Frequency: 433.92MHz_x000D_ Standby Power Consumption: 0.25W_x000D_ Music: 38_x000D_ Volume: 3 levels and mute_x000D_ Controllable Volume: 50dB/1m_x000D_ Receiving Distance: 150 meters (unobstructed in open space)_x000D_ Receiver Working Temperature: -10-+45_x000D_ Transmitter Operating Temperature: -20-+60_x000D_ Receiver Size: 78 x 54 x 20mm/ 3.07 x 2.13 x 0.79in_x000D_ Transmitter Size: 66 x 40 x 20mm/ 2.6 x 1.58 x 0.79in_x000D_ The transmitter does not need a battery, it is self generated by pressing PackageList: 2 x Doorbell 2 x Receiver 2 x Sticker Note: 1. The remote control distance is affected by the use environment, and the distance will vary due to different use environments._x000D_ 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._x000D_ 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.