Self-generating transmitter: No battery is needed. A finger press can trigger the generator to convert into electrical energy Not just a doorbell but also a pager: The elderly, children, and pregnant women have needs, just click to know, sleep at night with peace of mind Easily deal with various places: In villas/apartments/office buildings/hotels/nursing homes and other places 5 levels of adjustable volume whatever you want: The doorbell has five levels of volume, which can be adjusted freely. (Volume can be adjusted, light reminder) Anti-interference, no crosstalk: Digital circuit design, multiple sets of use will not cause cross talk, effectively avoiding the troubles caused by mutual interference between neighbors Specifications: Model: FA50 (86 Large Button) Music: 60 music tracks Volume: 5 levels of volume (adjustable to flashing light only) Transmitter: No batteries required, press to generate power Receiver: Light only when the bell rings Transmitter size: 86 x 86 x 22mm Receiver voltage: Plug in and use (AC110V/220V) Receiver size: 90 x 56 x 20mm Remote control distance: 150M in a straight line on open ground