AKG WMS 40 Mini Sport ISM1, UHF Wireless-System with bodypack transmitter and Headset microphone CKBT, non Diversity receiver with adjustable balanced jack output, HDAP Technoloiy(High Definition Audio Performance), up to 30 hours with one 1x AA Battery, LED status control on transmitter, Low Battery control on transmitter, On/Off/Mute switch on transmitter, three status LEDs on receiver, incl. condenser headset microphone CKBT, frequency ISM 1 863.100 MHz. No licence needed, free to use all over Europe.