Self-generating transmitter, no battery is needed, a finger press can trigger the generator to convert into electrical energyBarrier-free receiving distance can reach 150M in a straight line4 levels adjustable volume, which can be adjusted freely (Volume can be adjusted to mute)The transmitter is installed outside the door, the receiver is installed on the power socket, press the transmitter and ring the bell, and the receiver immediately rings and flashes to remindSpecification:Model: FA99Music: 36 music optionalVolume: 4 levels of volume adjustable (adjustable mute)Transmitter: no battery required, press to generate electricityReceiver: plug in the power supply (110-220V)Transmitter size: 70*46*24mmReceiver size: 91*59*25mmRemote control distance: straight line 150M on open groundPackage included:1 x EU Plug Receiver1 x Transmitter1 x English User Manual1 x Installation Tool Kit