Apple Macintosh Performa 5400 Series - Manual (Page 146)

Connecting a second monitor for video mirroring
You can connect a second, external monitor to your computer to display the
same images that are on the computer’s built-in monitor. Displaying your
computer’s images on a second monitor, called video mirroring, is useful for
presentations.
If you want to use video mirroring, you need the Apple External Video
Connector with an external monitor attached. If your computer doesn’t have a
connector installed, you can purchase the connector kit from an Apple-
authorized dealer and install it following the instructions that come with it.
The external monitor must use the same resolution and timing (refresh rate)
as the built-in monitor. Depending on what type of monitor you have added,
you may need to change the built-in monitor’s setting to one that the external
monitor is capable of displaying. This is done with the Monitors & Sound
control panel in the Control Panels folder in the Apple (K) menu.
Apple External Video Connector installed
145 If You Purchase Additional Equipment