The Gem Sound GMW61 is an affordable dual channel wireless microphone system featuring VHF high band operation (160-216MHz) and a super heterodyne receiver to ensure good performance in karaoke and presentation situations. Microphones operate on a standard 9V battery that provides up to eight hours of operation. Four frequencies available. Select frequency from dropdown menu (AB/CD/EF/GH).Frequency List:A-B 230.7 mhz, 254.6 mhzC-D 229.2 mhz, 252.6 mhzE-F 227.7 mhz, 251.6 mhzG-H 231.7 mhz, 255.6 mhz