Reference

Combinations and Functions with the Fn Key

Press and hold down the Fn key and another key simultaneously to perform a keyboard shortcut action.

For example, to turn off the sound: Fn+F2 → Press and hold down the Fn key, then press the F2 key.

Some keyboard functions can only be used while Windows is running.

Combination/Feature	Function
Fn + (F1)	Disables and enables the touch pad. [Details]
Fn + (F2)	Turns on and off the built-in speakers or the headphones.
Fn + / (F3/F4)	Press the button repeatedly to adjust the volume level of the built-in speakers and headphones. [Details] To increase the volume, press the Fn+F4 keys. To decrease the volume, press the Fn+F3 keys.
Fn + / (F5/ F6)	Press the button repeatedly to adjust the LCD brightness of your computer screen. [Details] To decrease lighting intensity, press the Fn+F5 keys. To increase lighting intensity, press the Fn+F6 keys.
Fn + (F7)	Switches the display output to an external display. Press the Fn+F7 keys several times to select the desired display output destination, and then press the Enter key to confirm. [Details]
Fn + (F12)	Cuts off power to most of your VAIO computer, including LCD and CPU (Hibernate mode).