United airlines noise reduction headphones

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avinash.salelkar

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Sep 17, 2017
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Does anyone know the pin outs for noise reduction headphones in united international business class? It has two pins- one a 3.5mm pin that is audio both channels and a second which is thinner. It seems the thinner one is for powering the noise reduction circuit. This one has three contacts so not sure why 3 as two should suffice. Also what voltage is to be applied? I tried 3V, 6V and 9V but got no noise reduction functionality.
 
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