Most laptop computers require a function key or software command to activate/deactivate the laptop video output signal. Usually, the activation/deactivation command acts as a toggle switch: repeat the command to display the image on the internal laptop display, the external display (projector) or both displays simultaneously.
Examples: Acer: Fn+F5, Dell: Fn+F8 will activate/deactivate laptop/external display.
Function key Function
1. Fn+F3 A panel for selecting a power scheme appears.
2. Fn+F4 Put the computer in standby mode
3. Fn+F5 Enable or disable the built-in wireless networking features and the bluetooth features.
4. Fn+F7 Switching the display output location
5. Fn+F8 Change the settings of the Ultra Navigation pointing device.
6. Fn+F9 Open the ThinkPad Easy Eject Utility screen. Buttons for the following choices are displayed:
7. Fn+F12 Put the computer into hibernation mode
8. Fn + PgUp Turn the Think Light on or off.
9. Fn+Home The computer display becomes brighter.
10. Fn+End The computer display becomes dimmer.