Specifications: Product Name: Bluetooth Transmitter Receiver. Protocol:RX:A2DP  AVRCPTX:A2DP. Operation Range: Up to 10m  (without any blocking objects). Battery:400MA. Working Hours:RX>10_H    TX>10_H. Charging  Hours:about 3 hours. Voltage:DC 5V. Input/output connection:SPDIF, 3.5MM stereo audio interface. LED indicator definition: - Red light is on: When the device is charging, it will automatically go out after being fully charged. - Blinking red: The device has a low battery alarm and the charge can be removed. - Red and blue lights flash alternately: The device is in RX receive mode (waiting for pairing). - The blue light flashes twice twice (cycle 2S:) The device is in the RX receive mode (reconnect mode). - The blue light is on: The device is in the RX receive mode (the connection is successful). No music play) - Fast blue light: The device is in TX receiving mode. (search for nearby Bluetooth devices) - The blue light flashes slowly: The device is in TX receiving mode. (Bluetooth is successfully connected) Charging:  This product has a built-in rechargeable battery for long-term standby and use. When the product is in normal use, “the red light flashes, indicating that it is in the low battery alarm mode and needs to be charged. (It is recommended to fully charge it before using it for the first time.) A. Plug one end of the Micro USB charging cable into the product charging port and the other end to the standard USB 5V power output port (such as mobile phone charger, computer USB interface). B. The red light is on when charging, and the red light is off after charging is completed. Note: 1. When the battery is too low or the quality of the charging power is poor, current interference noise may occur during charging. 2, often used for charging, will affect the battery life. 3, the product, please try not to low battery storage, low battery storage for a long time may cause the battery automatic protection can not supply power. Functional Operation: 1. Power on/off: long press the on/off button (the interval should not be lower than 3S). When the light is on, it means the boot is successful.    RX boot light effect: red and blue lights,    TX boot light effect: blue light flashes twice and once off (cycle 2S). 2. The device automatically enters the back-to-back pairing search state. When the device is turned on, the device automatically enters the connection state, and the 5S does not return to automatically enter the pairing state (the TX/RX lamp effect is different). 3. Quickly enter pairing mode. After the device is turned on, press the power button twice to quickly enter the pairing search status. 4. AUX/SPDIF mode switching: The device audio adopts manual switching mode, and the toggle switch to SPDIF is the optical fiber input/output mode. When the toggle switch is connected to AUX, the interface audio cable will automatically switch to AUX (input/output), and you can use AUX according to your preference. Or SPDIF mode. In SPDIF mode, the device plugs into the SPDIF IN port and implements the TX (transmit) function. It is also necessary to insert the SPDIF OUT port to implement the RX (receive) function. AUX Distinguishes: - In RX mode, AUX is connected to external speakers.