USB Bluetooth Transmitter Receiver: Transmitter mode: Transmit audio from non-Bluetooth audio sources (TV,PC,CD/DVD player, etc) to Bluetooth headset/speaker via 3.5mm audio cable. Receiving mode: Transmit the audio of the Bluetooth audio source (smartphone, tablet, Bluetooth TV) to the non-Bluetooth headset/speaker/car/home audio system through the 3.5mm audio cable. (NOTE:Only audio can be transmitted, video and files cannot be transmitted) Wide range of applications: This USB Bluetooth 5.0 adapter can be used for almost all devices with audio input/output (3.5mm auxiliary audio interface).When used with Bluetooth headsets or Bluetooth speakers, you can easily enjoy music and TV programs without affecting others and ensuring privacy. (USB 5V power supply, dont worry about running out of power when listening to music) USB audio transmission:Transmitter mode: Transmit audio through the USB port (wireless transmission). The audio is transmitted through the AUX port 3.5mm audio cable. Receiver mode: The audio is transmitted to the speaker through the AUX port 3.5mm audio cable. One Key Answering/hanging up calls:in Receiver mode, when you have an incoming call, press the button to answer the call hands-free One Key Switch Mode:Simply press a button to quickly switch transmitter/receiver mode.After this Bluetooth Transmitter Receiver adapter is powered on, red light in TX - Transmitter mode, blue light in RX - Receiver mode.