Fiio X3 - Micro SD Card and Headphone Outputs; Track Navigation and Indicator Lights; USB Port and Functionality

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9) Micro SD card slot: Standard micro SD card slot, supporting micro SD cards up to 256GB
10) Up / Previous track / Rewind: In"Now Playing" screen: press briefly to select the previous song
for playback, hold down to rewind the current song;
In menus: press briefly to choose the previous item (up) in menus.
11) Down / Next track / Fast forward: In "Now Playing" screen: press briefly to select the next song
for playback, hold down to fast forward through the current song;In menus: press briefly to choose
the next item (down) in menus.
12) Indicator light: Blue while working, red while charging, green when fully charged.
13) 3.5mm Headphone /Line/Coaxial output：The headphone out, line out and coaxial output
share the same port. You can toggle which mode you want to use under the "Select output" option
in the System Settings menu.
The headphone out also supports the use of CTIA standard (e.g. most smartphones) in-line
headsets. When using in-line controls, you can do the following：
Volume Up/Down：Briefly press the volume buttons to increase or decrease the volume by one
step. Hold to continually increase/decrease the volume until maximum volume/mute is set.
Play/Pause：Press the middle button once to pause. Press again to resume playing.
Skip to next track：Quickly press the middle button twice.
Skip to previous track：Quickly press the middle button 3 times.
Fast Forward：Quickly press the middle button 2 times, holding down the last press. Release the
button to resume playing.
Rewind：Quickly press the middle button 3 times, holding down the last press. Release the button
to resume playing.
14) Micro USB port (11 pin):
For data exchanging, battery charging and connection to docking FiiO devices
15) 2.5mm balanced headphone output: Supports 2.5mm TRRS balanced headphone