Sennheiser Infra Red IS410 Wireless Ultra-lightweight Assistive Listening Stereo Headphone System Connectivity Technology: Wireless Ideal for TV sound transmission,Max. Sound pressure level (active):125 dB. Cordless infra-red system with excellent sound quality. Balance control on the headphones for separately setting the volume level for the left and right ear. Lithium-Ion rechargeable battery pack ("accupack") for more than 16 hrs. of audio enjoyment. Transmits sound within a room, at a distance of up to 12 meters.