Self-generating transmitter, no battery is needed, a finger press can trigger the generator to convert into electrical energy Barrier-free receiving distance can reach 150M in a straight line 4 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 remind Specification: Model: FA99 Music: 36 music optional Volume: 4 levels of volume adjustable (adjustable mute) Transmitter: no battery required, press to generate electricity Receiver: plug in the power supply (110-220V) Transmitter size: 70*46*24mm Receiver size: 91*59*25mm Remote control distance: straight line 150M on open ground Package included: 1 x EU Plug Receiver 1 x Transmitter 1 x English User Manual 1 x Installation Tool Kit