This information is for the QX3/QX3+ and QX5 microscopes.
The Top lamp icon is located under the Control Panel in the main window and toggles the top lamp of the microscope on and off.
The Bottom lamp icon is located to the right of the Top lamp icon and toggles the bottom lamp of the microscope on and off.
If the top lamp is on and the Bottom lamp icon is clicked the top lamp will turn off and the bottom lamp will turn on, and vice-versa, if the bottom lamp is on and the Top lamp icon is clicked the bottom lamp will turn off and the top lamp will turn on.
The top and bottom lamps can be toggled on and off from the Controls menu in the main menu bar.
If the microscope is out of it's cradle, only the top lamp can be turned on and off.