2-in-1 Adapter: Turns any device with a 3.5mm audio jack into a Bluetooth transmitter or receiver. Choose between transmitter and receiver mode. Transmitter: Transmits music from a TV, PC/laptop, stereo system, etc. to a Bluetooth-enabled headphone, speaker, etc. When used as a transmitter, up to 4 receivers can be paired, allowing the audio signal to be sent to 2 Bluetooth devices simultaneously. Receiver: Transmits music, for example, from a smartphone via Bluetooth to a HiFi system or surround sound system. When used as a receiver, up to 8 transmitters can be paired, with the audio signal being received from one Bluetooth device at a time. Can be paired with any Bluetooth-enabled device (e.g., headphones, speakers). Audio input via the included 3.5mm audio cable. Bluetooth 4.1 (supports A2DP Bluetooth profile). APTX technology: for higher audio quality despite limited bandwidth with Bluetooth. Range of up to 10 meters. Built-in battery: easy charging with compatible USB chargers via micro-USB charging cable.