GTD Audio U-504H UHF Wireless Microphone System with 4 Hand held mics 4 Channel UHF Receiver with 4 Hand-held Microphones Individual volume controls on each Channel 400 feet ( 150 Meters ) Range One 1/4" Mixed output and four XLR Individual outputs Frequency range: 510Mhz - 560Mhz ( This wireless microphone unit is a fixed frequency unit, only one unit can work at one time. Multiple units can not work together and will cause interference with each other)