Press and hold the VOL + and VOL - buttons at the same time until appears on the screen.
To restore the original volume, press the VOL + button or the VOL - button.
You can mute audio from the system's speakers when headphones are disconnected from the headset jack.
To enable this setting, select the checkbox to set a checkmark.
You can hear audio by pressing the VOL + button or the VOL – button.