Feature:1. No Battery Required: Self generating wireless doorbell, wiring free, battery free, long distance transmission, two doorbells and one receiver, can be used for front and rear doors.2. Long Operating Range: Strong penetration, signal matching, do not worry about and next door cross line. Whether you use it in a few rooms away, it is always easy to be notified when someone calls from the door.3. 58 Ringtones: There are 58 optional ringtones, and the built in speaker can emit rich, clear and stereo sound. There are 4 adjustable levels of volume, and the flashing indicator light is also easy to notice.4. IP44 Waterproof: Premium materials to prevent itself from being affected by higher temperatures and interference. Could withstands various severe weather conditions, suitable for indoor and outdoor use.5. Used as Pager: It can not only be used as a doorbell, but also as a pager, suitable for babies, the elderly, pregnant women, sound and light reminders, convenient for the elderly and ear disease patients.Specification:Item Type: Self Generating DoorbellMaterial: ABSTransmitter Power Supply: Self generatingTransmitter Size: Approx. 63 x 63 x 20mm/2.48 x 2.48 x 0.79inTransmitter Working Temperature: -20C to +60CTransmitter Transmission Distance: Open places > apprrox. 150m/492ftTransmitter RF Frequency: 433MHzReceiver Power Supply: AC110-240V 50/60HzReceiver Power Consumption: 0.25WRingtones: 58Receiver Volume: 90dBReceiver Working Temperature: -10 to +45.Package List:2 x Push Button1 x Receiver2 x Sticker1 x ManualNote:Fault analysis:1, The doorbell does not ring: check whether the receiver is plugged in, whether the socket is energized.2, The transmission distance is short: iron doors, iron frames and other metal objects will affect the effective transmission distance. Prevent transmitters and receivers placed from metal objects. Walls and ceilings also affect the distance of transmission. Interference from other wireless devices, etc.