From Sennheiser website:
"The IS 410 is an ultra-lightweight infrared stereo stethoset TV listening system that enables the user to individually adapt the volume of TV sets, radios and hi-fi systems to his or her hearing ability. The transmitter connects easily to this equipment and transmits crystal-clear audio within a room. Operation of the stethoset headphone system is easy and intuitive. Balance and volume are set directly on the stethoset headphones. The transmitter features a compression button that further enhances speech intelligibility. Automatic on/off.

Features

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  Ideal for TV sound transmission

  
  


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  Cordless infra-red system with excellent sound quality

  
  


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  Transmits sound within a room, at a distance of up to 12 meters

  
  


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  Balance control on the headphones for separately setting the volume level for the left and right ear

  
  


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  Compression function ensures superior speech intelligibility and very good reproduction of music

  
  


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  Superior transmission reliability due to 2.3/2.8 MHz carrier frequencies

  
  


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  Lithium-Ion rechargeable battery pack ("accupack") for more than 16 hrs. of audio enjoyment

  
  


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  Transmitter recharges the headphones plus an additional accupack

  
  


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  Headphones automatically switch on and off when they are put on/removed

  
  


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  Includes short instructions for quick set-up

  
  


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  Very lightweight stethoset headphones, extremely comfortable to wear even for extended listening

  
  


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  Ideal for wearers of glasses"