Koss JR900 Cordless Stereo Headphones (Discontinued by Manufacturer) Provides Wireless Listening Transmits Through Walls Or Ceilings Multiple Source Capability With Additional Transmitters Closed Ear Cushions For Better Base and Isolation 20 to 20,000 Hz frequency response Includes RF (radio frequency) transmission headphone, transmitter, and AC power adapter Provides cordless listening from your stereo, video, or computer sound source; transmits through walls or ceilings Closed ear cushions for better bass and sound isolation Stereo/mono switch, power indicator, and volume control