HIGH PERFORMANCE TRANSMITTER: Ultra-low power consumption; uses a lithium battery that boasts 3 year maximum lifespan; IP55 dustproof and waterproof; working temperature ranges from -4 °F-140 °F; withstands various harsh weather conditions 1300 FT / 400 M WIRELESS RANGE: 2 plug-in receivers included; will not interfere with other equipment in your home or those of your neighbors; ensures that you will never miss any visitors, even if you are several rooms away 52 BEAUTIFUL CHIMES: 40 mm stereo speaker delivers rich and crisp sound; press the Next or Previous button to easily choose from 52 melodies; 5 adjustable volume levels, with a maximum volume of 115 dB; enjoy pleasant melodies whenever someone rings at your door MEMORY FUNCTION: Preserves your last set melody and volume level after a power outage; no need to reset to your previous settings; convenient and easy to use design for a better user experience EASY TO SET UP: Additional AVANTEK RB-1/CR-1 plug-in receivers c