Google uses sound for pairing - seems to work okay in reasonably sized room with all kinds of surfaces https://gigaom.com/2014/06/26/chromecast-will-use-ultraso

Google uses sound for pairing - seems to work okay in reasonably sized room with all kinds of surfaces https://gigaom.com/2014/06/26/chromecast-will-use-ultrasonic-sounds-to-pair-your-tv-with-your-friends-phones/ https://gigaom.com/2014/06/26/chromecast-will-use-ultrasonic...