In TX mode, double press button LL/HD after the device is connected, so to enable aptX LL First. Under this state, other Bluetooth codecs will be disabled except for aptX LL and SBC. Double press button LL/HD again to disable aptX LL First. Light SYATUS will stay constantly on following the corresponding Bluetooth codec after the device is reconnected. At this time, all supported codecs will be enabled. Short press button LL/HD to successively switch the codec.