-It is a unique wireless doorbell, the differences between other plug-in doorbells is the push button self-generating launcher, no battery or wire needed, it can provided itself the power after pushed; -It can reach up to around 200m in the open air, the push button transmitter is IP44 waterproof, acceptable to use outdoor; -Musical doorbell, with selection of 48 melodies, 6 level volumes to turn up/down; -LED indicator, you can add launchers or receivers for your need, it can be heared from any rooms rather than miss the visit; -Easy install, no wire needed, no worry about screwing up the wall, stick the launcher bell outdoor and plug in the receiver indoor, then it starts to work for your home convenience and security; Specification: Material: ABS Plastic Laucher: Approx. 75x42x22mm/ 2.95x1.65x0.87inch Receiver: Approx. 90x60x30mm/ 3.54x2.36x1.18inch Working Distance: 200m Voltage: AC110V-220V Plug: US Package Includes: 1 Set Wireless Doorbell Note: 1.Due to the manual measurement, there is a slight color and size difference between the above and the actual item. 2.Please keep the detector and receiver in sheltered places to avoid contact of both units form water and direct sunlight. 3.Clean the detective regularly with a damp cloth to avoid blockage of sensor by dirt; 4.Press the push button harder, or it may not generate enough power;