Folding Sport Wireless Sport Headphone Headset-Headphones (behind-the-neck) - wireless Stereo hifi Headphone for TV, VCD, PC , MP3 ,dvd with 3.5mm to 2.5mm adapter w/ Transmitter Wireless FM System: FM with Radio Carrier frequency: 85-108.5MHz Power supply of transmitter: 3 x AAA or DC 4.5V 100mA Power supply of headphone: 2 x AAA Auto mute and auto tuning function available for headphone