Unisar DH900 TV Listener | Wireless Digital TV Audio Assisted Listening Device System 2.4GHz wireless RF (radio frequency) digital technology (mono or stereo) Headset mute button turns off sound from transmitter and turns on built-in mic for amplifying conversations around you Compartment for charging extra battery Compatible with iPod/iPhone, CD/MP3 Players, Hi-Fi and TV sets. Volume control, 4 tone settings, Balance control