Astro Gaming MixAmp TXD Wireless Transmitter (for Astro A50 Gen 1/2 Headset ONLY). MixAmp TXD Top: Left Button: Power/Pairing Right Button: Dolby Headphone Virtual 7.1 Digital Surround On/Off MixAmp TXD - Rear: PWR: Connect the USB Power Cable from this port to a free port on your console or PC to power the MixAmp TxD and enable voice capability*. AUX: Auxiliary In. Plug your media device into this port with an optional 3.5mm cable in order to wirelessly stream audio to your A50 headset. Intended for use with MP3 players, phones, and PCs (when optical digital out is not available). OPT-OUT: Optical Out Pass through, use this input to connect your home theater system. OPT IN: Use this input to connect the Optical Cable from TV, PC, or console USB: Insert the USB Charging Cable into this socket, and attach the other end to the port on your A50s when not in use. This port is also utilized when updating to the latest firmware.