1、28 optional Melodies ringtones, and 4 levels of adjustable volume. Convenient for you to choose them randomly. 2、Support Voltage, 433.92MHZ Wireless frequency, easy and simple to install. 3、The ringing flashing design, can provide much convenience for hearing impaired people. 4、With strong signal and far transmission function. Up to 150 meters wireless range in open area, can reduce the influence of distance successfully. 5、Waterproof and moisture proof function, can be installed anywhere and anytime, no worry about the bad weather. Features: The ringing flashing design, can provide much convenience for hearing impaired people. With strong signal and far transmission function. Up to 150 meters wireless range in open area, can reduce the influence of distance successfully. Waterproof and moisture proof function, can be installed anywhere and anytime, no worry about the bad weather. Press to generate electricity, no battery required, is energy saving and practical in use. Specification: Material: ABS plastic Color: White Wireless Distance: Freely accessible 150 meters without interference in open area Ringtone: 28 chord music Model: Wireless electric doorbell Volume Adjustment: 4 levels controllable, ringing flashing Wireless Frequency: 433.92MHZ Use Environment: -10-+55 °C Waterproof Rating: IP68 Package List: 3 x Transmitter 3 x Receiver 3 x Double-Sided Sticker 1 x User Manual (For Model A Only) or 2 x Transmitter 3 x Receiver 2 x Double-Sided Sticker 1 x User Manual (For Model B Only)