What is the Rx switch on my TV streamer?

Your TV streamer has three switches on its front side. 'Tx', 'Off' and 'Rx'. To use your Audeara A-01's with your television, you should have the switch to 'Tx', to transmit sound from your television to your headphones. 

Receive or Rx mode will transfer the sound in the opposite direction from your smartphone to an older stereo or speaker.