Instead of using a battery, the button converts kinetic energy into electrical energy and sends a signal when pressed; don't worry if the battery has no power, so don't miss important visitorsThe 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 remindLong distance barrier-free 150m strong singal penetrationThe doorbell sound is not just a simple "ding dong" sound, it can also realize the free switching of 60 chord music, the sound quality is mellow, and it is pleasant to hear, press the doorbell, and the receiver rings and fashesThe doorbell has five levels of volume, which can be adjusted freelyDigital circuit design, multiple sets of use will not cause cross-talk, effectively avoiding the troubles caused by mutual interference between neighborsThrough different transmitter signals, let the receiver emit different bells to easily distinguish which door has visitors Specifications: Product Brand: CACAZIMusic: 60 music optionsProduct name: Self-powered Wireless DoorbellModel: FA96 (Type 86 Big Button)Volume: 5 levels (You can adjust it to flash only)Transmitter: no battery needed, press to generate electricityReceiver: Light comes on when the bell ringsReceiver: plug in the power supply (110V/220V)Transmitter size: 86*86*22mm, Receiver size: 90*56*20mmRemote control distance: 150M straight line distance on the barrier-free ground (data source factory experiment) Package included: 1 x Transmitter 2 x Receivers 1 x Installation Pack 1 x English User Manual