Features: Ringing flashing design, can provide much convenience for hearing impaired people. 38 optional Melodies ringtones, and 4 levels of adjustable volume. It is convenient for you to choose them randomly to meet your different needs. With strong signal and far transmission function. Up to 100 meters wireless range in open area, reduces the influence of distance successfully. Support AC 100V-240V Voltage, 433.92MHZ Wireless frequency, easy and simple to install. Waterproof and moisture proof design, can be installed anywhere and anytime, not considering the bad weather. Press to generate electricity without battery, energy saving and practical in use. Specifications: Color: Black Voltage: 110-240V Plug Type: EU Plug, US Plug, UK Plug (optional) Optional Model: Model A(3Transmitter&3Receiver), m odel B(2Transmitter&3Receiver) (optional) Transmitter Size: Approx.45x70mm/1.8x2.8in Receiver Size : Approx. 50x67mm/2x2.6in Model: Wireless electric doorbell Material: ABS plastic Wireless Distance: Freely accessible 100 meters without interference in open area Ringtone: 38 chord music Volume Adjustment: 4 levels controllable, ringing flashing Rated Voltage: AC100-240V 50/60HZ 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)