Expandable for an Unlimited Number of Users Note: This system requires a human language interpreter, it does not translate automatically. low power consumption design for long playtime up to 30hours battery life It operates in the license-free 902-927 MHz ISM band. ISM band requires no user licensing Carrier Frequency:902 907 912 917 922 927MHz,Range of up to 200m outdoors/50m indoors (depending on environmental conditions)