Before using the unit for the first time, we recommend charging the battery in the Marlin unit. Charging is performed by inserting the 3.5mm side of the charging cable into the Marlin unit and the USB side to a USB port as shown below. Please note there is notch in the unit to ensure the connection is in the correct orientation.

If charging is in progress, a red LED with blink. When charging is completed, the red LED will turn off. The bone conduction headset draws battery from the Marlin unit and does not need to be charged.  

Clear the headphone jack of water before inserting the charge cable or the headset cable. Never attempt to charge or connect while there is water in the headphone jack. The Marlin is only designed to be used with the provided cable and headsets. Usage of third party headsets and cables are not recommended and will void the warranty.