GTD Audio U-35H UHF Wireless Microphone System Karaoke mic with 2 microphones 2 Channel Receiver with 2 Microphones Individual volume controls on each Channel 300 feet ( 100 Meters ) Range, Carrier Frequency: UHF 520~560MHz This microphone unit is a fixed frequency unit, only one unit can work at one time, using multiple units will cause interfere with each other.