2400-2483MHZ band for international free license 8-95 channels for multiple groups use the system at an area without interference. Digitally Synthesized Frequencies Powered by built-in rechargeable Lithium battery for long time continuous use. Charging time: 4-6 hours Battery life: 15-20 hours Up to 150 meters (500ft) line-of-sight reception range Belt-clip for hand-free operation LCD display for battery status and channel Hi-fi acoustic quality and high tone quality, CD sound quality Each transmitter available for unlimited receivers With MP3 Player function Available for Simultaneous interpretation,8-channel used for 6-version simultaneous interpretation,95-channel available for more than 20 version interpretation.