1. With 1 push button transmitter and 2 plug in receivers perfect for classroom, small 2-story homes or large apartments. 2. Easy install and use can pair more transmitter and receivers if needed. 3. With 58 Melodies & 5 Level Volume Meet your different needed for different music and different volume. 4. Ultra-low power consumption design, sustainable use of Energy. can work in -30°C to 70°C.