Advent AW823C Wireless Outdoor Speaker with 900MHz Transmitter and Receiver Indoor/Outdoor System Phase-Locked Loop (PLL) guarantees crystal clear audio reproduction Automatic Level Controls (ALC) prevents sudden drastic changes in volume Superior Performance with 900MHz Wireless Advantage The 3-in-1 Power/Volume/Tuning button puts the essential controls in one place Tripod feet and water-resistant design makes the speaker natural for outdoor settings