What does the indicator light on the HD4 front panel mean?
If it's on and solid, this means the HD4 is powered on, and currently connected to a Bluetooth-enabled device.
If your source is currently sending the HD4 an aptX signal, the LED indicator on the rear panel will illuminate orange instead of white.
If it's on and blinking, this means the HD4 is powered on but not currently connected to a device.
If it's off (and HD4 is powered on), this means Bluetooth is in standby and not connected to a device. The HD4, however, is still visible to your device, so simply connect using your device and the HD4 will automatically wake up.