Sun Microsystems Enterprise 250 Owner's Manual page 261

Keyboard LEDs
Four LEDs on the Sun Type-5 keyboard are used to indicate the progress and results
of POST diagnostics. These LEDs are on the Caps Lock, Compose, Scroll Lock, and
Num Lock keys, as shown below.
Scroll Lock Num Lock
LED LED
Caps Lock LED Caps Lock LED Compose
(UNIX keyboard) (standard keyboard) LED
To indicate the beginning of POST diagnostics, the four LEDs briefly light all at once.
The monitor screen remains blank, and the Caps Lock LED blinks for the duration of
the testing.
If the system passes all POST diagnostic tests, all four LEDs light again and then go
off. Once the system banner appears on the monitor screen, the keyboard LEDs
assume their normal functions and should no longer be interpreted as diagnostic
error indicators.
If the system fails any test, one or more LEDs will light to form an error code that
indicates the nature of the problem.
Note – The LED error code may be lit continuously, or for just a few seconds, so it
is important to observe the LEDs closely while POST is running.
Chapter 11 Diagnostics and Troubleshooting 243