Set includes 1 plug in mains receiver 1 battery operated portable receiver and 1 bell push 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 plug in and battery operated variable volume control 150m range choice of 32 melodies current melody playback function waterproof bell push battery included flashing strobe chime s