Saful Wireless Ring Door 28 Ringtons Touch proof 150M Remote Plug me Home Doorbell|Doorbells(black) product is a smart doorbell which is unlike the traditional wireless doorbell. It is simple & easy to operate, has stable transmission signal, fit for apartment, villas, home, hospital and many places product is according to the rules of the frequencies using of our country.It won't produce harmful electromagneti interference. main function 1.simple design, elegant, chic style 2.ultra-low-power design, energy saving and sustainable use 3.long distance remote control, stable signal 4.28 polyphonic ring tones for optional,25- dB 5.Adjustable indoor ring volume 6.150M Receiving distanc(in open area) 7. ed to last up to 25 years 8.change the is easy specification Indoor receiver Voltage Range:AC - V Operating temperature:-10 - 55 degree Outdoor transmitter Voltage Range: 12V 23AAlkaline batteries*1 Operating temperature:-20 - 65 degree Transmission distance:100 meters in open area Operating Frequency:433.92MHz200KHz :0.1W Volume:25- dB