Audiovox MVIRHS Wireless Infrared Headset for WHS100 Headphone System (Discontinued by Manufacturer) Additional headphones for use with Audiovox WHS100 wireless headphone system or VOH6XX series of flipdown pods; wireless transmitter not included 25-foot range, 35 to 18,000 Hz frequency response High-quality FM (frequency modulation) transmission; 60 dB signal-to-noise ratio Battery-saving auto shutoff after 3 minutes with no signal Uses 2 AAA batteries (not included)