This door chime can automatically learn the frequency of other mip system modules including up to four additional bell pushpir transmitters and four door chime receivers mip system this product can be programmed to add other mip door chime and bell push modules up to 4 transmitter and 4 receiver mips modules can be programmed at once easy diy installation 150m range unobstructed choice of 32 melodies waterproof bell push with nameplate battery included chime requires 3 x aa batteries not