The UGREEN 3.5mm wireless adapter is a two-in-one Bluetooth transmitter and receiver that can transmit and receive via TX and RX modes. Note: RX mode is the only mode in which phone calls are supported; TX mode is not. You can convert non-Bluetooth stereo devices, such as TVs, PCs, home theater systems, and automobile stereos, to Bluetooth-enabled devices by using an aux bluetooth transmitter. Simply pair your old devices with the Bluetooth converter to start enjoying wireless speakers' excellent sound quality. Stable Connection: The UGREEN Bluetooth transmitter uses less power and provides a fast and stable transmission thanks to Bluetooth 5.0 technology. The 3.5mm Bluetooth wireless transmitter can play for up to 5.5 hours in RX mode and 8 hours in TX mode. Furthermore, the Aux connector can be connected to