Spectec SDV-841/842 - Manual (Page 23)

Disabling the Virtual Display
Choosing the configuration named "(Disable Virtual Display)" restores your
device's display settings to their factory default values.
Alternatively, if your device should behave abnormally or become unusable
after switching to a new virtual display configuration, simply press the device
RESET button. This will return the device to the factory default display
settings. This action will not harm your device but you may loose unsaved data
in any running programs. Note that this behavior can be overridden by
checking the Preserve after Reset when Modifying Configuration Properties .
This option should be used with great caution.
If you still experience problems you may need to perform a hard reset as a last
resort. This will restore your device to its factory setting. Note: This will result in
a loss of transient AND stored data. Consult your device owner manual for
instruction for performing a hard reset.