Detailed Description  Features:  1) UHF wireless stereo headphone with 864MHz ISM band 2) Operation distance up to 100 meters with latest UHF/RF wireless technology  3) Several headphones can be used simultaneously with one transmitter  4) Built-in 40mm mylar speaker  5) Auto mute and auto tuning function available for headphone 6) Active noise reduction system for crystal clear sound 7) Double PLL system for ultimate frequency stability Specifications:  1) System: UHF/RF  2) Carrier frequency:   For Europe: 863.5, 864, 864.5MHz  For US: 914, 914.5, 915 MHz  3) Modulation: FM  4) Mode: stereo  5) Frequency response: 30 - 20,000Hz 6) Power supply of transmitter: DC12V 150mA 7) Power supply of headphone: 2 x AAA