1、Self Generating: Press the doorbell with your finger, kinetic energy is converted to electricity, instantly transmitting wireless signals, do not need battery. 2、Long Range: Adopting 433MHz wireless signal, strong penetration, can penetrate 3‑4 doors, receiving distance in open areas can reach 150 meters. 3、38 Melodies: Electronic doorbell with 38 melodies can be switched freely, the ringtones are melodious, 3 volume levels can be adjusted according to your needs. 4、IP44 Waterproof: The waterproof level of the transmitter reaches IP44, can withstand the harshest weather, safe and durable, has a long service time. 5、Multifunction: Not just the doorbell, can also turn into a pager, suitable for old people, babies and pregnant women who sleep alone, reliable to use. 6、Easy Installation: Easy to install, no battery and no wiring required, can be fixed with screws, low power dissipation, convenient for using, save your time and energy. Item Type: Wireless Doorbell Material: ABS Operating Frequency: 433.92MHz Standby Power Consumption: 0.25W Melodies: 38 Volume: 3 Levels, Mute Controllable Volume: ≥50dB/1m Receiving Distance: ≥150m / 164yd  (In Open Space) Receiver Working Temperature: -10℃ to +45℃ Transmitter Operating Temperature: -20℃ to +60℃ Receiver Size: Approx. 78x54x20mm / 3.1x2.1x0.8in Transmitter Size: Approx. 66x40x20mm / 2.6x1.6x0.8in The transmitter does not need battery, it is self generated by pressing 1 x Wireless Doorbell 2 x Receiver 1 x Sticker