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 4392MHz 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.